runtime: detail the method comment

Change the comment to make more conformable to the function implementation.

Change-Id: I8461e2f09824c50e16223a27d0f61070f04bd21b
GitHub-Last-Rev: c25a8493d3938b38e2c318f7a7b94c9f2eb11bb4
GitHub-Pull-Request: golang/go#27404
Reviewed-on: https://go-review.googlesource.com/c/go/+/132477Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

src/runtime/proc.go

@@ -2203,7 +2203,7 @@ func execute(gp *g, inheritTime bool) {
 }
 
 // Finds a runnable goroutine to execute.
-// Tries to steal from other P's, get g from global queue, poll network.
+// Tries to steal from other P's, get g from local or global queue, poll network.
 func findrunnable() (gp *g, inheritTime bool) {
 	_g_ := getg()