CI: workaround for github actions bug

Github Actions checkout@v2 fails to properly cleanup state in self-hosted runners
which leads to errors from prior CI runs.

actions/checkout#385

Adding the created submodule directory to gitignore should hopefully
prevent this from happening: actions/checkout#424 (comment).

.github/workflows/parallel_tests.yml

@@ -97,7 +97,6 @@ jobs:
       run: |
         docker system prune -af --filter "until=72h"
         docker builder prune -af --filter "until=72h"
-        [[ ! -z "$GITHUB_WORKSPACE" ]] && rm -rf $GITHUB_WORKSPACE
 
   build_and_check_fork: # Forked repos can't use self-hosted test suite - just checkout and run make check
     if: github.repository != 'panda-re/panda'

.gitignore

@@ -166,3 +166,7 @@ panda/plugins/syscalls_logger/test/test_fw
 
 # Local files to be gitignored
 local
+
+# Workaround for CI to avoid github checkout@v2 actions bug when auto-generating documentation
+auto_pydoc
+auto_pydoc/pandare