Update actions/cache requirement to v2.1.3 (#16)

Updates the requirements on [actions/cache](https://github.com/actions/cache) to permit the latest version.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](https://github.com/actions/cache/commits/0781355a23dac32fd3bac414512f4b903437991a)

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

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

.github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
           key: ${{ env.key }}
 
       - name: Cache extensions
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.3
         with:
           path: ${{ steps.cache-env.outputs.dir }}
           key: ${{ steps.cache-env.outputs.key }}

.github/workflows/mutation.yml

@@ -47,7 +47,7 @@ jobs:
         run: echo "COMPOSER_CACHE_DIR=$(composer config cache-dir)" >> $GITHUB_ENV
 
       - name: Cache dependencies installed with composer
-        uses: actions/[email protected].1
+        uses: actions/[email protected].3
         with:
           path: ${{ env.COMPOSER_CACHE_DIR }}
           key: php${{ matrix.php }}-composer-${{ hashFiles('**/composer.json') }}

.github/workflows/static.yml

@@ -33,7 +33,7 @@ jobs:
         run: echo "COMPOSER_CACHE_DIR=$(composer config cache-dir)" >> $GITHUB_ENV
 
       - name: Cache dependencies installed with composer
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.3
         with:
           path: ${{ env.COMPOSER_CACHE_DIR }}
           key: php${{ matrix.php }}-composer-${{ hashFiles('**/composer.json') }}