Correct restore-key expression

Author: jneira

.github/workflows/test.yml

@@ -89,7 +89,7 @@ jobs:
             ${{ env.CABAL_STORE_DIR }}
           key: ${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
           restore-keys: |
-            ${{ runner.os }}-${{ matrix.ghc }}-build-$${ hashFiles('cabal.project') }}
+            ${{ runner.os }}-${{ matrix.ghc }}-build-${{ hashFiles('cabal.project') }}
             ${{ runner.os }}-${{ matrix.ghc }}-build-
             ${{ runner.os }}-${{ matrix.ghc }}