Change cabal version to 2.4, to match GHC 8.6.5

.github/workflows/build-macos-package.yml

@@ -9,11 +9,11 @@ jobs:
     strategy:
       matrix:
         os: [macOS-latest]
-        cabal: ["3.2"]
+        cabal: ["2.4"]
         ghc: ["8.6.5"]
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
     - uses: actions/setup-haskell@v1.1.1
       id: setup-haskell-cabal