maint: remove workaround for legacy LuaRocks bug.

* local.mk (dist_luastddebug_DATA): Move
lib/std/debug_init/init.lua from here...
(dist_luastd_DATA): ...to lib/std/debug_init.lua.
(luastddebugdir, dit_luastddebug_DATA): Remove.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>