cmd/compile: update TestNexting golden file

This change updates the expected output of the gdb debugging session
in the TestNexting internal/ssa test, aligning it with the changes
introduced in CL 147360.

Fixes the longtest builder.

Change-Id: I5b5c22e1cf5e205967ff8359dc6c1485c815428e
Reviewed-on: https://go-review.googlesource.com/c/147957


Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>