doc: add missing article

Change-Id: I73fdc793bbc3ffe9ace1bfa78799f84c31630d61
Reviewed-on: https://go-review.googlesource.com/48391Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.9.html

@@ -233,7 +233,7 @@ type T1 = T2
   Profiles produced by the <code>runtime/pprof</code> package now
   include symbol information, so they can be viewed
   in <code>go</code> <code>tool</code> <code>pprof</code>
-  without binary that produced the profile.
+  without the binary that produced the profile.
 </p>
 
 <p> <!-- CL 38343 -->
@@ -978,4 +978,3 @@ version of gccgo.
     </p>
 
 </dl><!-- time -->
-