A+C: fixed doubled entry

Delete an erroneously doubled name in both files. Once is enough.

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/118420043

AUTHORS

@@ -287,7 +287,6 @@ Michael Teichgräber <mteichgraeber@gmx.de>
 Michał Derkacz <ziutek@lnet.pl>
 Miek Gieben <miek@miek.nl>
 Mihai Borobocea <MihaiBorobocea@gmail.com>
-Mihai Borobocea <MihaiBorobocea@gmail.com>
 Mikael Tillenius <mikti42@gmail.com>
 Mike Andrews <mra@xoba.com>
 Mike Rosset <mike.rosset@gmail.com>

CONTRIBUTORS

@@ -410,7 +410,6 @@ Michael Teichgräber <mteichgraeber@gmx.de> <mt4swm@googlemail.com>
 Michał Derkacz <ziutek@lnet.pl>
 Miek Gieben <miek@miek.nl> <remigius.gieben@gmail.com>
 Mihai Borobocea <MihaiBorobocea@gmail.com>
-Mihai Borobocea <MihaiBorobocea@gmail.com>
 Mikael Tillenius <mikti42@gmail.com>
 Mike Andrews <mra@xoba.com>
 Mike Rosset <mike.rosset@gmail.com>