runtime: fix comments in tracetype.go

They seem to have been copy and pasted from tracestack.go without being
updated.

Change-Id: I6a6a69645a778fe8e6e8a2f4a80429f20e90162e
Reviewed-on: https://go-review.googlesource.com/c/go/+/674215
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: felixge

src/runtime/tracetype.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Trace stack table and acquisition.
+// Trace type table.
 
 package runtime
 
@@ -13,7 +13,7 @@ import (
 	"unsafe"
 )
 
-// traceTypeTable maps stack traces (arrays of PC's) to unique uint32 ids.
+// traceTypeTable maps types to unique uint32 ids.
 // It is lock-free for reading.
 type traceTypeTable struct {
 	tab traceMap