CL 158457 added a duplicate entry for the ",\n" -> "," replacement to
gofmtLineReplacer. Remove the duplicate.

Change-Id: I17684fcd19cbc96fa7a7b53bf7c1a6382bf1114f
Reviewed-on: https://go-review.googlesource.com/c/158619
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>