testing/gdb-embedded: remove aport

@maribu you maintain gdb-embedded. I just pushed gdb-multiarch as a subpackage of the gdb aport. gdb-multiarch supports all architectures supported by GDB and should therefore also support the GDB architectures currently packaged by gdb-embedded. I never used gdb-embedded though and was therefore wondering if gdb-multiarch also covers your use-case if so I would suggest removing gdb-embedded in favor of gdb-multiarch.