Updated GitHub CI

Author: colemancda

.github/workflows/swift.yml

@@ -4,16 +4,12 @@ jobs:
 
   macos:
     name: macOS
-    strategy:
-      matrix:
-        swift: [5.7.1]
-        os: [macos-latest]
-    runs-on: ${{ matrix.os }}
+    runs-on: macos-latest
     steps:
     - name: Install Swift
       uses: slashmo/install-swift@v0.3.0
       with:
-        version: ${{ matrix.swift }}
+        version: 5.7.1
     - name: Checkout
       uses: actions/checkout@v2
     - name: Swift Version