fix: update existing comment whenever possible

Author: jgravois

.github/workflows/terraform-plan.yml

@@ -60,8 +60,17 @@ jobs:
       - name: Create tf-summarize markdown file
         run: tf-summarize -md tfplan >> tf-summary.md
 
+      - name: Find Comment
+        uses: peter-evans/find-comment@b30e6a3c0ed37e7c023ccd3f1db5c6c0b0c23aad # v4.0.0
+        id: fc
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          comment-author: "github-actions[bot]"
+          body-includes: CHANGE
+
       - name: Create PR comment with course-grained plan summary
         uses: peter-evans/create-or-update-comment@e8674b075228eee787fea43ef493e45ece1004c9 # v5.0.0
         with:
+          comment-id: ${{ steps.fc.outputs.comment-id }}
           issue-number: ${{ github.event.number }}
           body-path: "./terraform/tf-summary.md"