Failing unit test on master branch (since at least 2022)

One test, FontsAndCollationChangesMergeCleanly, has been failing on the master branch since at least September 2022. I (Robin Munn) went as far back in Git history as I could get the tests to run, and found that I could get the tests to run on commit 7d1b3e3ff (from 2022-09-22) but any earlier and I couldn't get the project to build. But as far back as 7d1b3e3ff, the FontsAndCollationChangesMergeCleanly test has been failing.

I don't know yet if the test is written incorrectly and should be fixed (or just removed), or if it's a real bug that we need to fix. But it's been failing for nearly three years, well before the move from Mercurial 3 to Mercurial 6.5.1 (in fact, 7d1b3e3ff, the oldest commit I could successfully run, uses Mercurial 3.0.3.4), so the cause of the failure is probably NOT any changes to Mercurial since then.

If anyone is able to run the tests further back than 7d1b3e3ff, that would help in finding the commit that caused the test to break, which may help us figure out a solution.