Re-vendor openapiv2 to fix case change breaking Docker build

[ryanbrainard]

gnostic/openapiv2 lowercased their repo name, which is breaking the Docker build in this project:

$ docker build 'https://github.com/opsgenie/kubernetes-event-exporter.git#master'                
[+] Building 1.9s (8/9)                                                                                                                                              
 => CACHED [internal] load git source https://github.com/opsgenie/kubernetes-event-exporter.git#master                                                          0.0s
 => [internal] load metadata for gcr.io/distroless/base:latest                                                                                                  0.0s
 => [internal] load metadata for docker.io/library/golang:1.17                                                                                                  1.2s
 => [builder 1/4] FROM docker.io/library/golang:1.17@sha256:b983574376a29f21ccba0a90f1e1f31864d084cee73295b774305b792b31b8bd                                    0.0s
 => [stage-1 1/2] FROM gcr.io/distroless/base                                                                                                                   0.0s
 => CACHED [builder 2/4] ADD . /app                                                                                                                             0.0s
 => CACHED [builder 3/4] WORKDIR /app                                                                                                                           0.0s
 => ERROR [builder 4/4] RUN CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -mod=vendor -a -o /main .                                                           0.7s
------
 > [builder 4/4] RUN CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -mod=vendor -a -o /main .:
#7 0.631 vendor/k8s.io/client-go/discovery/discovery_client.go:31:2: cannot find package "." in:
#7 0.631        /app/vendor/github.com/googleapis/gnostic/openapiv2
------
executor failed running [/bin/sh -c CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -mod=vendor -a -o /main .]: exit code: 1

This change deletes vendor/github.com/googleapis/gnostic/OpenAPIv2, re-runs go mod vendor, and adds the new vendor/github.com/googleapis/gnostic/openapiv2. Note, it was done two commits to deal with MacOS's case insensitivity that otherwise would not detect the change.

Correctly working build on this fork/branch:

$ docker build 'https://github.com/ryanbrainard/kubernetes-event-exporter.git#fix-vendor-openapi'                                                              1 ↵
[+] Building 2.9s (11/11) FINISHED                                                                                                                                   
 => CACHED [internal] load git source https://github.com/ryanbrainard/kubernetes-event-exporter.git#fix-vendor-openapi                                          0.0s
 => [internal] load metadata for docker.io/library/golang:1.17                                                                                                  2.8s
 => [internal] load metadata for gcr.io/distroless/base:latest                                                                                                  0.0s
 => [auth] library/golang:pull token for registry-1.docker.io                                                                                                   0.0s
 => [stage-1 1/2] FROM gcr.io/distroless/base                                                                                                                   0.0s
 => [builder 1/4] FROM docker.io/library/golang:1.17@sha256:b983574376a29f21ccba0a90f1e1f31864d084cee73295b774305b792b31b8bd                                    0.0s
 => CACHED [builder 2/4] ADD . /app                                                                                                                             0.0s
 => CACHED [builder 3/4] WORKDIR /app                                                                                                                           0.0s
 => CACHED [builder 4/4] RUN CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -mod=vendor -a -o /main .                                                          0.0s
 => CACHED [stage-1 2/2] COPY --from=builder --chown=nonroot:nonroot /main /kubernetes-event-exporter                                                           0.0s
 => exporting to image                                                                                                                                          0.0s
 => => exporting layers                                                                                                                                         0.0s
 => => writing image sha256:7eeea331f6b86d8047c63ac7f1519b6543749e9fd0099d9b0278e9ee2a51186f                                                                    0.0s

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