[CI] Don't autolabel insubstantial PRs 'pleasereview' (#1293)

* Don't label insubstantial PRs 'pleasereview'

* Update auto-label-prs.yml

* Update auto-label-prs.yml

polkadot/.github/workflows/auto-label-prs.yml

-name: Label new PRs
+name: Label PRs
 on:
   pull_request:
     types: [opened,ready_for_review]
@@ -7,14 +7,15 @@ jobs:
   label-new-prs:
     runs-on: ubuntu-latest
     steps:
-      - name: Label new drafts
+      - name: Label drafts
         uses: andymckay/labeler@master
         if: github.event.pull_request.draft == true
         with:
           add-labels: 'A3-inprogress'
-      - name: Label new PRs
+          remove-labels: 'A0-pleasereview'
+      - name: Label PRs
         uses: andymckay/labeler@master
-        if: github.event.pull_request.draft == false
+        if: github.event.pull_request.draft == false && ! contains(github.event.pull_request.labels.*.name, 'A2-insubstantial')
         with:
           add-labels: 'A0-pleasereview'
           remove-labels: 'A3-inprogress'