translations: rename Norwegian translation from nb_NO to nb

This puts us more in line with other projects that don't attach the country
code to the language code.

$ du -sh /usr/share/locale/nb*/LC_MESSAGES
3.5M    /usr/share/locale/nb/LC_MESSAGES
132K    /usr/share/locale/nb_NO/LC_MESSAGES

Signed-off-by: Dan McGee <dan@archlinux.org>

TRANSLATORS

@@ -30,7 +30,7 @@ Italian (it):
 	Giovanni Scafora <giovanni@archlinux.org>
 Kazakh (kk):
 	Baurzhan Muftakhidinov <baurthefirst@gmail.com>
-Norwegian (nb_NO):
+Norwegian (nb):
 	Hans-Kristian Arntzen <maister@archlinux.us>
 Polish (pl):
 	Mateusz Herych <heniekk@gmail.com>

lib/libalpm/po/LINGUAS

@@ -9,7 +9,7 @@ fr
 hu
 it
 kk
-nb_NO
+nb
 pl
 pt_BR
 ro

po/LINGUAS

@@ -9,7 +9,7 @@ fr
 hu
 it
 kk
-nb_NO
+nb
 pl
 pt_BR
 ro