Remove -DBUILD_WITH_HTTP_SERVER=OFF from cmake command line

[paoloczi]

Using -DBUILD_WITH_HTTP_SERVER=OFF no longer has any effect and should be removed from the cmake command line when building Shasta. It generates the following cmake warning message:

CMake Warning:
  Manually-specified variables were not used by the project:

    BUILD_WITH_HTTP_SERVER

However this message is innocuous as the build proceeds anyway.