Bump actions/cache from v1 to v2.1.4

Bumps [actions/cache](https://github.com/actions/cache) from v1 to v2.1.4.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v1...26968a0)

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

Author: dependabot[bot]

.github/workflows/docker.yml

@@ -25,7 +25,7 @@ jobs:
           override: true
 
       - name: Cache cargo registry
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.4
         with:
           path: ~/.cargo/registry
           key: docker-registry-${{ hashFiles('**/Cargo.lock') }}
@@ -34,7 +34,7 @@ jobs:
             docker-
 
       - name: Cache cargo index
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.4
         with:
           path: ~/.cargo/git
           key: docker-index-${{ hashFiles('**/Cargo.lock') }}
@@ -43,7 +43,7 @@ jobs:
             docker-
 
       - name: Cache cargo build
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.4
         with:
           path: target
           key: docker-build-${{ hashFiles('**/Cargo.lock') }}