Bump actions/cache from v2 to v2.1.4

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>

Author: dependabot[bot]

.github/workflows/main.yml

@@ -20,7 +20,7 @@ jobs:
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: 'latest'
-      - uses: actions/cache@v2
+      - uses: actions/cache@v2.1.4
         with:
           path: ~/.cabal
           key: cabal--${{ matrix.ghc }}-${{ hashFiles('*/*.cabal') }}
@@ -53,7 +53,7 @@ jobs:
           enable-stack: true
           stack-version: 'latest'
           stack-setup-ghc: true
-      - uses: actions/cache@v2
+      - uses: actions/cache@v2.1.4
         with:
           path: |
             .stack-work