chore(cleanup): remove "experimental" note
the note was made 6 years ago and is redundant now.
@@ -6,6 +6,4 @@ This package includes auto-generated clients for the logging v2 API.
Use the handwritten logging client (in the parent directory,
cloud.google.com/go/logging) in preference to this.
-This code is EXPERIMENTAL and subject to CHANGE AT ANY TIME.
-
