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/ci.yml

@@ -13,7 +13,7 @@ jobs:
       - name: Check out repository code
         uses: actions/checkout@v2
       - name: Do some action caching
-        uses: actions/cache@v2.1.4
+        uses: actions/cache@v2.1.5
         with:
           path: vendor
           key: ${{ runner.os }}-gem-${{ hashFiles('Gemfile', '*.gemspec') }}