Don't create/unarchive groups on member removal messages (#5618)

[iequidoo]

Close #5618 Although the task is about "group left" messages, i think it's ok to not create/unarchive groups for all member removal messages. At least currently for DC-style groups create_group() already avoids group creation for any member removals. Then, if we don't consider member removal messages important enough to create groups, why unarchive already existing ones.