dockerfile: update cni to 1.6.0

[crazy-max]

closes #5232

https://github.com/containernetworking/plugins/releases/tag/v1.6.0

[crazy-max]

Seems we got a bunch of test failure in buildkit and frontend: https://github.com/moby/buildkit/actions/runs/11916250858/job/33210058740?pr=5533#step:8:1844

=== FAIL: frontend TestFrontendIntegration/TestRefReadDir/worker=containerd-1.6 (1.43s)
    frontend_test.go:240: 
        	Error Trace:	/src/frontend/frontend_test.go:240
        	            				/src/util/testutil/integration/run.go:97
        	            				/src/util/testutil/integration/run.go:211
        	Error:      	Received unexpected error:
        	            	Unavailable: connection error: desc = "error reading server preface: read unix @->/tmp/bktest_buildkitd3532617275/buildkitd.sock: read: connection reset by peer"
        	            	github.com/moby/buildkit/util/stack.Enable
        	            		/src/util/stack/stack.go:82
        	            	github.com/moby/buildkit/util/grpcerrors.FromGRPC
        	            		/src/util/grpcerrors/grpcerrors.go:204
        	            	github.com/moby/buildkit/util/grpcerrors.UnaryClientInterceptor
        	            		/src/util/grpcerrors/intercept.go:41
        	            	google.golang.org/grpc.(*ClientConn).Invoke
        	            		/src/vendor/google.golang.org/grpc/call.go:35
        	            	github.com/moby/buildkit/api/services/control.(*controlClient).ListWorkers
        	            		/src/api/services/control/control_grpc.pb.go:130
        	            	github.com/moby/buildkit/client.(*Client).ListWorkers
        	            		/src/client/workers.go:31
        	            	github.com/moby/buildkit/client.(*Client).Build
        	            		/src/client/build.go:32
        	            	github.com/moby/buildkit/frontend.testRefReadDir
        	            		/src/frontend/frontend_test.go:235
        	            	github.com/moby/buildkit/util/testutil/integration.testFunc.Run
        	            		/src/util/testutil/integration/run.go:97
        	            	github.com/moby/buildkit/util/testutil/integration.Run.func2.1
        	            		/src/util/testutil/integration/run.go:211
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1690
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1700
        	            	failed to list workers
        	            	github.com/moby/buildkit/client.(*Client).ListWorkers
        	            		/src/client/workers.go:33
        	            	github.com/moby/buildkit/client.(*Client).Build
        	            		/src/client/build.go:32
        	            	github.com/moby/buildkit/frontend.testRefReadDir
        	            		/src/frontend/frontend_test.go:235
        	            	github.com/moby/buildkit/util/testutil/integration.testFunc.Run
        	            		/src/util/testutil/integration/run.go:97
        	            	github.com/moby/buildkit/util/testutil/integration.Run.func2.1
        	            		/src/util/testutil/integration/run.go:211
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1690
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1700
        	            	listing workers for Build
        	            	github.com/moby/buildkit/client.(*Client).Build
        	            		/src/client/build.go:34
        	            	github.com/moby/buildkit/frontend.testRefReadDir
        	            		/src/frontend/frontend_test.go:235
        	            	github.com/moby/buildkit/util/testutil/integration.testFunc.Run
        	            		/src/util/testutil/integration/run.go:97
        	            	github.com/moby/buildkit/util/testutil/integration.Run.func2.1
        	            		/src/util/testutil/integration/run.go:211
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1690
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1700

[tonistiigi]

also #5462 (comment)