chore(deps): update actions/cache requirement to v2.1.5 (#230)

Updates the requirements on [actions/cache](https://github.com/actions/cache) to permit the latest version.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](https://github.com/actions/cache/commits/1a9e2138d905efd099035b49d8b7a3888c653ca8)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
           node-version: '12'
 
       - name: Cache node_modules
-        uses: actions/[email protected].4
+        uses: actions/[email protected].5
         id: cached-node_modules
         with:
           path: |
@@ -34,7 +34,7 @@ jobs:
           python-version: '3.8'
 
       - name: Cache pip
-        uses: actions/cache@v2
+        uses: actions/cache@v2.1.5
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}-${{ hashFiles('requirements-constraints.txt') }}-${{ hashFiles('dev-requirements.txt') }}