daily stubtest: also pin to updated commit (#14645)

Author: JelleZijlstra

.github/workflows/daily.yml

@@ -50,6 +50,9 @@ jobs:
           check-latest: true
       - name: Install dependencies
         run: pip install -r requirements-tests.txt
+      # Temporary to get @disjoint_base support; can remove once mypy 1.18 is released
+      - name: Install mypy from git
+        run: pip install git+https://github.com/python/mypy.git@116b92bae7b5dbf5e6bd36fd9b0c6804973e5554
       - name: Run stubtest
         run: python tests/stubtest_stdlib.py