include ruby in cache line

Author: robkooper

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
       - uses: actions/cache@v1
         with:
           path: vendor/bundle
-          key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
+          key: ${{ runner.os }}-gems-${{ matrix.ruby}}-${{ hashFiles('**/Gemfile.lock') }}
           restore-keys: |
             ${{ runner.os }}-gems-
       - name: Set up Ruby ${{ matrix.ruby }}