Bump actions/cache from v2 to v2.1.4 (open-telemetry#1518)

Bumps [actions/cache](https://github.com/actions/cache) from v2 to v2.1.4.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2...26968a0)

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

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

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
  echo "GOPATH=$(go env GOPATH)" >> $GITHUB_ENV
  echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
  - name: restore cache
- uses: actions/cache@v2
+ uses: actions/cache@v2.1.4
  env:
  cache-name: cache-go-mod
  with: