chore(deps): pin dependencies

.github/workflows/ci.yml

@@ -5,15 +5,15 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
 
       - name: Set up Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@e9aba2c848f5ebd159c070c61ea2c4e2b122355e # v2
         with:
           python-version: "3.9"
 
       - id: cache
-        uses: actions/cache@v1
+        uses: actions/cache@f5ce41475b483ad7581884324a6eca9f48f8dcc7 # v1
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt', '**/test_requirements.txt') }}
@@ -29,6 +29,6 @@ jobs:
         run: coverage xml
 
       - name: Upload coverage to CodeCov
-        uses: codecov/codecov-action@v1
+        uses: codecov/codecov-action@29386c70ef20e286228c72b668a06fd0e8399192 # v1
         with:
           file: ./coverage.xml