cmd/stringer: fix package godoc

CL 191309 broke it by adding a newline before the package clause.

Change-Id: Ic039649734ae086a891227b5926e028fe7e62325
Reviewed-on: https://go-review.googlesource.com/c/tools/+/204137
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

cmd/stringer/stringer.go

@@ -59,9 +59,10 @@
 // The -linecomment flag tells stringer to generate the text of any line comment, trimmed
 // of leading spaces, instead of the constant name. For instance, if the constants above had a
 // Pill prefix, one could write
-//   PillAspirin // Aspirin
+//
+//	PillAspirin // Aspirin
+//
 // to suppress it in the output.
-
 package main // import "golang.org/x/tools/cmd/stringer"
 
 import (