ci: remove confusing message now that --ast-check is added
This extra message was intended to help contributors by clarifying
what to do when they hit a `zig fmt` failure, but now AST errors are
also emitted here and the message may actually introduce confusion.
Remove it for now.
e125ead2b1Andrew Kelley committed on 6/15/2021, 9:27:56 PMparent76584ad