As a part of the work in SERVER-95023 we're cleaning up concurrency suites' exclude lists and tags. does_not_support_causal_consistency is not a tag that should be a part of the excluded set of tags in multi stmt txn suites.

map_reduce_drop.js was originally excluded from the multi stmt transaction concurrency suites via the does_not_support_causal_consistency because mapReduce did not support afterClusterTime - however this doesn't matter in multi stmt txn suites anyway.

Re-enabling the test in multi stmt txn suites caused the test to fail, but not because of the mapReduce command - see comments for diagnosis and patch link. We should be able to restructure this test to get it to run.

Also, since mapReduce is deprecated, and since this test has caused other problems in the past (SERVER-77039), we may want to delete this test altogether.