Remove typing workaround for functools.cache

[hannes-ucsc]

We can revert 830b94f since upstream python/typeshed#15139 was fixed.

[achave11-ucsc]

Assignee to investigate how we would incorporate the upstream fix.

[hannes-ucsc]

Mypy bundles typeshed. This PR updates mypy's copy of typeshed to include the fix we need. PR was recently merged into master. Expecting upcoming version >= 1.19.2 of mypy to include the fix.

Leave in Triage until version drops. Once it does, assignee to revert the commit with the workaround, reproduce the original issue (some mypy error) with our current version of mypy (1.19.0), then upgrade mypy, which should fix the issue. File PR with changes.