runtime: delete repeated word

Change-Id: I0d7005481fc61b4c7f3286674c022334c8c0cae0
Reviewed-on: https://go-review.googlesource.com/c/go/+/424494
Reviewed-by: hopehook <hopehook@qq.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: hopehook <hopehook@qq.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index f73a3a82..633d181 100644
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -684,7 +684,7 @@
 	//
 	//    assistDuration * procs * (utilization + idleUtilization)
 	//
-	// In this case, we *include* idle utilization, because that is additional CPU time that the
+	// In this case, we *include* idle utilization, because that is additional CPU time that
 	// the GC had available to it.
 	//
 	// In effect, idle GC time is sort of double-counted here, but it's very weird compared