chore(deps): bump actions/cache from 2.1.5 to 2.1.6

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.5 to 2.1.6.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2.1.5...v2.1.6)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/test.yml

@@ -69,7 +69,7 @@ jobs:
         with:
           submodules: true
 
-      - uses: actions/cache@v2.1.5
+      - uses: actions/cache@v2.1.6
         with:
           path: ~/.npm
           key: ${{ matrix.os }}-${{ matrix.node-version }}-${{ hashFiles('**/package-lock.json') }}