ci: install typed-ast

Author: daviddrysdale

.github/workflows/typing.yml

@@ -19,6 +19,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install mypy==0.921 types-protobuf==3.19.21
+          pip install typed-ast==1.5.5
 
       - name: Execute run_stubtest.py
         run: |
@@ -40,6 +41,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install mypy==0.921 types-protobuf==3.19.21
+          pip install typed-ast==1.5.5
 
       - name: Run mypy
         run: |