Pin actions/checkout action to b4ffde6 (#18)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://togithub.com/actions/checkout) | action |
pinDigest | -> `b4ffde6` |

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Author: lettuce-bot[bot]

.github/workflows/auto-merge.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout source
-        uses: actions/checkout@v4
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
 
       - name: Create app token
         id: create-app-token