Bump actions/cache from v2.1.4 to v2.1.5

Bumps [actions/cache](https://github.com/actions/cache) from v2.1.4 to v2.1.5.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2.1.4...1a9e213)

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

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
             - ubuntu-latest
         steps:
             - uses: actions/checkout@v2
-            - uses: actions/cache@v2.1.4
+            - uses: actions/cache@v2.1.5
               with:
                 key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
                 path: ${{ env.HOME }}/go/pkg/mod