chore: specify git user email

yw leah

.github/workflows/update.yml

···
       - name: Setup Git
         run: |
           git config --global user.name "GitHub Actions"
-          git config --global user.email "[e-mail]"
+          git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
 
       - name: Update Lockfile
         run: nix flake update --commit-lock-file

.mailmap

···
+GitHub Actions <41898282+github-actions[bot]@users.noreply.github.com> <[e-mail]>