Bump actions/checkout to v4 (#105)

Author: davdroman

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
           - 5.9
     steps:
       - name: Git Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Test Library
         uses: mxcl/xcodebuild@v2

.github/workflows/format.yml

@@ -14,7 +14,7 @@ jobs:
     name: swiftformat
     runs-on: macos-13
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Format
         run: swiftformat .
       - uses: stefanzweifel/git-auto-commit-action@v4