Update tagbot.yml

Author: t-bltg

.github/workflows/tagbot.yml

@@ -29,4 +29,4 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           ssh: ${{ secrets.TAGBOT_KEY }}
-          branch: master  # FIXME: select `v2` on release of Plots 2.x
+          branch: v2