cmd/internal/objabi: regenerate RelocType stringer file

cmd/internal/objabi: regenerate RelocType stringer file

reloctype_strings.go is out-of-date since CL 462035, regenerate it.

Found while working on CL 461737.

Change-Id: I5cf910ab14c3618d6653c87861a4d53d3c91feff
Reviewed-on: https://go-review.googlesource.com/c/go/+/473875
Auto-Submit: Quim Muntal <quimmuntal@gmail.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>