Merge #21010: refactor: remove straggling boost::mutex usage
f827e151a2ce96e14aadb9e7d25045fe0a8afbd2 refactor: remove straggling boost::mutex usage (fanquake)
Pull request description:
After the merge of #18710, the linter is warning:
A new Boost dependency in the form of "boost/thread/mutex.hpp" appears to have been introduced:
^---- failure generated from test/lint/lint-includes.sh
#18710 removed `boost/thread/mutex.hpp` from lint-includes, however in the interim #19337 was merged, which introduced more `boost::mutex` usage.
Given we no longer use `boost::mutex`, just remove the double lock test and remaining includes.
ACKs for top commit:
Code review ACK f827e151a2ce96e14aadb9e7d25045fe0a8afbd2