Similar issues workflow explicit permission (#4040)

Explicitly add issues read permissions to similar issues workflow for
the minimum required access.
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.github/workflows/similarissues.yml

@@ -7,6 +7,8 @@ on:
 jobs:
   getSimilarIssues:
     runs-on: ubuntu-latest
+    permissions:
+      issues: read
     outputs:
       message: ${{ steps.getBody.outputs.message }}
     steps: