go_faq: typo fix

R=rsc
CC=golang-dev
https://golang.org/cl/962043

doc/go_faq.html

@@ -363,7 +363,7 @@ indicate.
 
 <p>
 Still, there is room for improvement. The compilers are good but could be
-better, many librarise need major performance work, and the garbage collector
+better, many libraries need major performance work, and the garbage collector
 isn't fast enough yet (even if it were, taking care not to generate unnecessary 
 garbage can have a huge effect).
 </p>