chore(deps): pin actions/checkout action to (#2)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://togithub.com/actions/checkout) | action |
pinDigest | -> `ee0669b` |

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.github/workflows/fly-deploy.yaml

@@ -17,7 +17,7 @@ jobs:
     name: Deploy app
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
       - uses: superfly/flyctl-actions/setup-flyctl@master
         with:
           version: 0.1.54