build: bump actions/cache from 2.1.5 to 2.1.6 (#2765)

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)

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

.github/workflows/deploy.yml

@@ -64,7 +64,7 @@ jobs:
 
       # Cache files between builds
       - name: Setup | Cache Cargo
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           path: |
             ~/.cargo/registry