ci: bump pytype to 2022.03.29 This is as far as we can go without running into issues with the vendored `attr` package. I tried updating that to the latest, and not only did it not fix the issue, but test-util.py failed due to some poking at `attr` internals that apparently is no longer valid. The `libcst` package is now pinned to what I have locally because trying to install the latest (0.4.7) complains that it can't find the Rust compiler. We should probably use a requirements file instead (and/or figure out why it can't find the Rust compiler), but I don't feel like dealing with another side quest.

--- a/contrib/heptapod-ci.yml	Wed Jul 13 12:47:40 2022 -0400
+++ b/contrib/heptapod-ci.yml	Wed Jul 13 17:13:33 2022 -0400
@@ -89,7 +89,7 @@
       - hg -R /tmp/mercurial-ci/ update `hg log --rev '.' --template '{node}'`
       - cd /tmp/mercurial-ci/
       - make local PYTHON=$PYTHON
-      - $PYTHON -m pip install --user -U pytype==2021.04.15
+      - $PYTHON -m pip install --user -U libcst==0.3.20 pytype==2022.03.29
     variables:
         RUNTEST_ARGS: " --allow-slow-tests tests/test-check-pytype.t"
         HGTEST_SLOWTIMEOUT: "3600"