cmd/stringer: fix package godoc
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 <4f40cda291c5f9634e1affd3db44947af61f705c@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools