Remove references to the Bazel flag `--distinct_host_configuration`.
If you are not yet on Bazel 6.0 you can close this and I won't migrate you, but do note the the delta between Bazel 5 and the next release is growing. Also, the internal LSC may also send CLs that you'll need to tell me to revert. Thanks! What needs to be done to merge this? It will be imported by copybara, run more CI internally and then automatically merged.
Part of https://github.com/bazelbuild/bazel/issues/17731.