chore: stop trying to auto-merge dependabot PR's (aws#4202)

It cannot work unless we can somehow get an auto-approval (from an authorized principal) in, too.

.mergify.yml

@@ -22,18 +22,6 @@ pull_request_rules:
       - "#changes-requested-reviews-by=0"
       - status-success~=AWS CodeBuild us-east-1
       - status-success=Semantic Pull Request
-  - name: automatically merge dependabot
-    actions:
-      comment:
-        message: Thanks for keeping us safe, @dependabot! ❤️
-      merge:
-        strict: smart
-        method: squash
-        strict_method: merge
-      delete_head_branch: {}
-    conditions:
-      - author~=dependabot(-preview)?\[bot\]
-      - status-success~=AWS CodeBuild us-east-1
   - name: comment checklist
     actions:
       comment: