Build Tools: Don't send AppVeyor notifications on Slack on repeated s…

…uccessful builds.

See #44276.



git-svn-id: https://develop.svn.wordpress.org/trunk@44599 602fd350-edb4-49c9-b593-d223f7449a82

appveyor.yml

@@ -29,5 +29,7 @@ notifications:
   - provider: Slack
     incoming_webhook:
       secure: CmhfxrWwgtwzO/kXoZWXRUB/Jh05AQ7DvOhToqtpm6dN1wBDp9+VnNqxldpv34uPd09vuUk4Nu/NQFkIswuZA5NYfIFJIFWqwnZExQFzTBA=
+    on_build_success: false
+    on_build_failure: true
     on_build_status_changed: true
     template: Build <{{buildUrl}}|#{{buildNumber}}> (<{{commitUrl}}|{{commitId}}>) of {{repositoryName}}@{{branch}} by {{commitAuthor}} {{status}} in {{duration}}