.github/workflows: bump create-pull-request to 8.0.0

Bump peter-evans/create-pull-request to 8.0.0 to ensure compatibility
with actions/checkout 6.x.

Updates #cleanup

Signed-off-by: Mario Minardi <mario@tailscale.com>

.github/workflows/update-flake.yml

@@ -35,7 +35,7 @@ jobs:
           private-key: ${{ secrets.CODE_UPDATER_APP_PRIVATE_KEY }}
 
       - name: Send pull request
-        uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e #v7.0.8
+        uses: peter-evans/create-pull-request@98357b18bf14b5342f975ff684046ec3b2a07725 #v8.0.0
         with:
           token: ${{ steps.generate-token.outputs.token }}
           author: Flakes Updater <noreply+flakes-updater@tailscale.com>

.github/workflows/update-webclient-prebuilt.yml

@@ -32,7 +32,7 @@ jobs:
 
       - name: Send pull request
         id: pull-request
-        uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e #v7.0.8
+        uses: peter-evans/create-pull-request@98357b18bf14b5342f975ff684046ec3b2a07725 #v8.0.0
         with:
           token: ${{ steps.generate-token.outputs.token }}
           author: OSS Updater <noreply+oss-updater@tailscale.com>