context: don't talk about tools that don't exist

This comment has been the source of much confusion and broken dreams. We
can add it back if a tool ever gets released.

Updates #16742

Change-Id: I4b9c179b7c60274e6ff1bcb607b82029dd9a893f
Reviewed-on: https://go-review.googlesource.com/130876Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/context/context.go

@@ -210,8 +210,7 @@ func Background() Context {
 // TODO returns a non-nil, empty Context. Code should use context.TODO when
 // it's unclear which Context to use or it is not yet available (because the
 // surrounding function has not yet been extended to accept a Context
-// parameter). TODO is recognized by static analysis tools that determine
-// whether Contexts are propagated correctly in a program.
+// parameter).
 func TODO() Context {
 	return todo
 }