Remove unused `# type: ignore`s (#12531)

Over time we've begun to use newer versions of mypy, typeshed, stub
packages---and of course we've improved our own annotations. This makes
some type ignore comments no longer necessary. I have removed them.

There was one exception: a module that imports `select.epoll`. The
ignore is redundant on Linux, but I've kept it ignored for those of us
who work on the source tree using not-Linux. (#11771)

I'm more interested in the config line which enforces this. I want
unused ignores to be reported, because I think it's useful feedback when
annotating to know when you've fixed a problem you had to previously
ignore.

* Installing extras before typechecking

Lacking an easy way to install all extras generically, let's bite the bullet and
make install the hand-maintained `all` extra before typechecking.

Now that https://github.com/matrix-org/backend-meta/pull/6 is merged to
the release/v1 branch.

1 files changed, 1 insertions, 0 deletions

diff --git a/changelog.d/12531.misc b/changelog.d/12531.misc
new file mode 100644
index 0000000000..412fc9b6dc
--- /dev/null
+++ b/changelog.d/12531.misc
@@ -0,0 +1 @@
+Remove unused `# type: ignore`s.