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] <[email protected]>

Author: dependabot[bot]

Diff for: .github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Restore cargo cache
-      uses: actions/cache@v2.1.4
+      uses: actions/cache@v2.1.5
       with:
         path: |
           ~/.cargo/registry