Auto merge of #26224 - mcast:doc-travis2buildbot, r=steveklabnik

Suggesting this because I was confused by what is now visible from the Travis CI / buildbot split.

Found the hint  in bors comments on d911936
Couldn't find anything on https://internals.rust-lang.org/

Author: bors

.travis.yml

@@ -16,6 +16,11 @@ before_script:
 script:
   - make tidy
 
+# Real testing happens on http://buildbot.rust-lang.org/
+#
+# See https://github.com/rust-lang/rust-buildbot
+#     CONTRIBUTING.md#pull-requests
+
 notifications:
   email: false