Update TagBot.yml

Based on https://discourse.julialang.org/t/ann-required-updates-to-tagbot-yml/49249.

Author: tkoolen

.github/workflows/TagBot.yml

@@ -1,9 +1,12 @@
 name: TagBot
 on:
-  schedule:
-    - cron: 0 * * * *
+  issue_comment:
+    types:
+      - created
+  workflow_dispatch:
 jobs:
   TagBot:
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
     runs-on: ubuntu-latest
     steps:
       - uses: JuliaRegistries/TagBot@v1