fix: Release please action checks out repo on release for build

Author: AngelOnFira

.github/workflows/release-please.yml

@@ -19,6 +19,10 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           release-type: simple
 
+      - name: Checkout
+        if: ${{ steps.release.outputs.release_created }}
+        uses: actions/checkout@v2
+
       - uses: game-ci/unity-builder@v2
         if: ${{ steps.release.outputs.release_created }}
         env:
@@ -34,4 +38,4 @@ jobs:
         if: ${{ steps.release.outputs.release_created }}
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: gh release upload ${{ steps.release.outputs.tag_name }} Rivet.unitypackage
+        run: gh release upload ${{ steps.release.outputs.tag_name }} Rivet.unitypackage