doc/go_faq: fix grammar

Change-Id: Idbd6c97d754e3565aeade4d9e8011a76e8da19c2
GitHub-Last-Rev: 22e917e5ca429d76506346841e5b3c93c2a5f3fb
GitHub-Pull-Request: golang/go#31439
Reviewed-on: https://go-review.googlesource.com/c/go/+/171885Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go_faq.html

@@ -2082,8 +2082,8 @@ At the beginning of the project we considered using LLVM for
 our performance goals.
 More important in retrospect, starting with LLVM would have made it
 harder to introduce some of the ABI and related changes, such as
-stack management, that Go requires but not are not part of the
-standard C setup.
+stack management, that Go requires but are not part of the standard
+C setup.
 A new <a href="https://go.googlesource.com/gollvm/">LLVM implementation</a>
 is starting to come together now, however.
 </p>