build(deps): bump actions/cache from 2.1.5 to 2.1.6 (#2023)

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](https://github.com/actions/cache/compare/v2.1.5...v2.1.6)

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

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

.github/workflows/pr.yml

@@ -74,7 +74,7 @@ jobs:
         uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.golang }}
-      - uses: actions/cache@v2.1.5
+      - uses: actions/cache@v2.1.6
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go-${{ matrix.golang }}-${{ hashFiles('**/go.sum') }}