runtime: fix typo in the templateThread godoc

Change-Id: Ie8d563d39b88ab1631bc150d7d5bdbf1aa400f76
GitHub-Last-Rev: d092c8c8eb886fd9abad9bdaed7330a6cbd7f9a4
GitHub-Pull-Request: golang/go#25716
Reviewed-on: https://go-review.googlesource.com/116115Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

src/runtime/proc.go

@@ -1942,7 +1942,7 @@ func startTemplateThread() {
 	newm(templateThread, nil)
 }
 
-// tmeplateThread is a thread in a known-good state that exists solely
+// templateThread is a thread in a known-good state that exists solely
 // to start new threads in known-good states when the calling thread
 // may not be a a good state.
 //