internal/trace/tracev2: adjust comment for consistency

Adjust the EvGoStatus comment to use the term M ID in favor of thread ID
in order to be consistent with the documentation for the other events.

Change-Id: Ie9f6d52df6eea809682a33aa2bc9922a57fe03db
Reviewed-on: https://go-review.googlesource.com/c/go/+/694618
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Michael Knyszek <[email protected]>
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: felixge

src/internal/trace/tracev2/events.go

@@ -45,7 +45,7 @@ const (
 	EvGoSyscallBegin      // syscall enter [timestamp, P seq, stack ID]
 	EvGoSyscallEnd        // syscall exit [timestamp]
 	EvGoSyscallEndBlocked // syscall exit and it blocked at some point [timestamp]
-	EvGoStatus            // goroutine status at the start of a generation [timestamp, goroutine ID, thread ID, status]
+	EvGoStatus            // goroutine status at the start of a generation [timestamp, goroutine ID, M ID, status]
 
 	// STW.
 	EvSTWBegin // STW start [timestamp, kind, stack ID]