completion: remove redundant __git_compute_all_commands() call

During lazy-initialization of the lists of all commands and porcelain commands the function __git_compute_all_commands() is called twice. The relevant part of the call sequence looks like this: __git_compute_porcelain_commands() __git_compute_all_commands() <finds list of all commands uninitialized> __git_list_all_commands() <initializes list of all commands> __git_list_porcelain_commands() __git_compute_all_commands() <finds list of all commands already initialized, does nothing> <filters porcelains from list of all commands> Either one of the two calls could be removed and the initialization of both command lists would still work as a whole, but let's remove the call from __git_compute_porcelain_commands(), because this way __git_list_porcelain_commands() will keep working in itself. Signed-off-by: SZEDER Gábor <szeder@ira.uka.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>