Improve library team mention message for consistency (#395)

Author: yaahc

highfive/configs/rust-lang/rust.json

@@ -199,7 +199,7 @@
             "reviewers": ["@rust-lang/miri"]
         },
         "library": {
-            "message": "Thank you for submitting a new PR for the library teams! If this PR contains a stabilization of a library feature that has not already completed FCP in its tracking issue, introduces new or changes existing unstable library APIs, or changes our public documentation in ways that create new stability guarantees then please comment with `r? rust-lang/libs-api @rustbot label +T-libs-api` to request review from a libs-api team reviewer. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary",
+            "message": "Hey! It looks like you've submitted a new PR for the library teams!\n\nIf this PR contains changes to any `rust-lang/rust` public library APIs then please comment with `r? rust-lang/libs-api @rustbot label +T-libs-api` to request review from a libs-api team reviewer. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.\n\nExamples of `T-libs-api` changes:\n\n* a stabilization of a library feature\n* introducing new or changes existing unstable library APIs\n* changes to  public documentation in ways that create new stability guarantees",
             "reviewers": []
         }
     },