runtime: fix typo in runqput comment

Change-Id: Idd88a1d9420545e3e326f8e3b57a38d8c7515555
GitHub-Last-Rev: 59528f552238eb4070cb9a66c1dbfafd6bc3808d
GitHub-Pull-Request: golang/go#25779
Reviewed-on: https://go-review.googlesource.com/116935Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/proc.go

@@ -4777,7 +4777,7 @@ func runqempty(_p_ *p) bool {
 const randomizeScheduler = raceenabled
 
 // runqput tries to put g on the local runnable queue.
-// If next if false, runqput adds g to the tail of the runnable queue.
+// If next is false, runqput adds g to the tail of the runnable queue.
 // If next is true, runqput puts g in the _p_.runnext slot.
 // If the run queue is full, runnext puts g on the global queue.
 // Executed only by the owner P.