ci: set actions/checkout to v4 (#23)

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## This PR
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- Just sets actions/checkout to be more lenient

### Related Issues
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Signed-off-by: Nicklas Lundin <[email protected]>

Author: nicklasl

.github/workflows/ci.yaml

@@ -12,14 +12,14 @@ jobs:
   Tests:
     runs-on: macOS-latest
     steps:
-    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
+    - uses: actions/checkout@v4
     - name: Build and Test
       run: swift test
 
   SwiftLint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
+    - uses: actions/checkout@v4
     - name: GitHub Action for SwiftLint
       uses: norio-nomura/[email protected]
       with: