doc/go1.7.html: avoid term of art

Rather than saying "stop-the-world", say "garbage collection pauses".

Change-Id: Ifb2931781ab3094e04bea93f01f18f1acb889bdc
Reviewed-on: https://go-review.googlesource.com/25018Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

doc/go1.7.html

@@ -377,9 +377,9 @@ packages.
 </p>
 
 <p>
-Stop-the-world times should be significantly lower for programs with
-large numbers of idle goroutines, substantial stack size fluctuation,
-or large package-level variables.
+Garbage collection pauses should be significantly shorter than they
+were in Go 1.6 for programs with large numbers of idle goroutines,
+substantial stack size fluctuation, or large package-level variables.
 </p>
 
 <h2 id="library">Core library</h2>