MANUAL: minor grammar fix

Noticed a typo reading through the docs.

Closes #3069

docs/MANUAL

@@ -866,7 +866,7 @@ ENVIRONMENT VARIABLES
   If the host name matches one of these strings, or the host is within the
   domain of one of these strings, transactions with that node will not be
   proxied. When a domain is used, it needs to start with a period. A user can
-  specify that both www.example.com and foo.example.com should not uses a
+  specify that both www.example.com and foo.example.com should not use a
   proxy by setting NO_PROXY to ".example.com". By including the full name you
   can exclude specific host names, so to make www.example.com not use a proxy
   but still have foo.example.com do it, set NO_PROXY to "www.example.com"