[dev.typeparams] runtime: remove tracebackdefers

tracebackdefers is used for scanning/copying deferred functions'
arguments. Now that deferred functions are always argumentless,
it does nothing. Remove.

Change-Id: I55bedabe5584ea41a12cdb03d55ec9692a5aacd9
Reviewed-on: https://go-review.googlesource.com/c/go/+/325916


Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>