ci: gpg commit signing for cron-update-rust.yml

Author: notmandatory

.github/workflows/cron-update-rust.yml

@@ -15,6 +15,11 @@ jobs:
         with:
           app_id: ${{ secrets.APP_ID }}
           private_key: ${{ secrets.APP_PRIVATE_KEY }}
+      - uses: crazy-max/ghaction-import-gpg@v5
+        with:
+          gpg_private_key: ${{ secrets.GPG_PRIVATE_KEY }}
+          git_user_signingkey: true
+          git_commit_gpgsign: true
       - name: Update rust-version to use latest stable
         run: |
           set -x
@@ -36,8 +41,8 @@ jobs:
         uses: peter-evans/create-pull-request@v6
         with:
           token: ${{ steps.generate-token.outputs.token }}
-          author: Update Rustc Bot <bot@example.com>
-          committer: Update Rustc Bot <bot@example.com>
+          author: Github Action <github@bitcoindevkit.org>
+          committer: Github Action <github@bitcoindevkit.org>
           branch: create-pull-request/update-rust-version
           title: |
             ci: automated update to rustc ${{ env.rust_version }}