dependabot: auto-merge requires on pull_request types

Auto-merge appears to function correctly with `pull_request` with types,
allowing it to authenticate and operate within the context of the target
repository. Without this, a 401 error is returned due to insufficient scope.

Signed-off-by: Seena Fallah <seenafallah@gmail.com>

Author: clwluvw

content/code-security/tutorials/secure-your-dependencies/automating-dependabot-with-github-actions.md

@@ -159,7 +159,9 @@ You can instead use {% data variables.product.prodname_actions %} and the {% dat
 ```yaml copy
 {% data reusables.actions.actions-not-certified-by-github-comment %}
 name: Dependabot auto-merge
-on: pull_request
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
 
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   contents: write