Bump actions/cache from 2.1.5 to 2.1.6

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](actions/cache@v2.1.5...v2.1.6)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/build.yaml

@@ -19,7 +19,7 @@ jobs:
         with:
           fetch-depth: 0
 
-      - uses: actions/[email protected].5
+      - uses: actions/[email protected].6
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
@@ -64,7 +64,7 @@ jobs:
         with:
           fetch-depth: 0
 
-      - uses: actions/[email protected].5
+      - uses: actions/[email protected].6
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}