Update blazor-issue-processing.yml (#33925)

Author: guardrex

.github/workflows/blazor-issue-processing.yml

@@ -7,6 +7,7 @@ on:
       - 'aspnetcore/blazor/**'
 jobs:
   process-blazor-issue:
+    if: github.event.label.name == 'blazor/subsvc'
     runs-on: ubuntu-latest
     permissions:
       issues: write