ci: drop approve step from Dependabot auto-merge (#156)

The approve step requires "Allow GitHub Actions to create and approve
pull requests" at the repo level, which is off here, so the workflow
fails on approve and the auto-merge step never runs. Without branch
protection requiring reviews, the approve was cosmetic anyway — the
auto-merge step alone gates on CI, which is the actual safety check.

Author: jeremy

.github/workflows/dependabot-auto-merge.yml

@@ -19,18 +19,6 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
 
       # CI is the safety gate — auto-merging action updates is circular.
-      - name: Approve patch and minor updates (excluding actions)
-        if: >-
-          (
-            steps.metadata.outputs.update-type == 'version-update:semver-patch' ||
-            steps.metadata.outputs.update-type == 'version-update:semver-minor'
-          ) &&
-          steps.metadata.outputs.package-ecosystem != 'github_actions'
-        run: gh pr review --approve "$PR_URL"
-        env:
-          PR_URL: ${{ github.event.pull_request.html_url }}
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Enable auto-merge for patch and minor updates (excluding actions)
         if: >-
           (