Drop non-standard compliant way of selecting api version
We currently allow passing the api version using a version string in the Accept: HTTP header. This is not compliant with the HTTP standard and is not actually needed since we currently only have one API version and no plans to add v3 in the foreseeable future.
Fixes #33787 - Drop Accept Header handling for API version
The API controller has been abusing the Accept header to define which
version of the API should be used. This is not compliant with the HTTP
spec1 which specifies that this header should be used to indicate
acceptable media types by the client.
Any clients currently passing the header should not be affected as the
default version of the API is v2. There are no plans currently to create
API v3, and even if it will eventually be developed, users will be able
to use the route to indicate which version they wish to use.