submodule--helper: remove unused SUPPORT_SUPER_PREFIX flags

Remove the SUPPORT_SUPER_PREFIX flag from "add", "init" and
"summary". For the "add" command it hasn't been used since [1],
likewise for "init" and "summary" since [2] and [3], respectively.

As implemented in 74866d7 (git: make super-prefix option,
2016-10-07) the SUPPORT_SUPER_PREFIX flag in git.c applies for the
entire command, but as implemented in 89c8626 (submodule helper:
support super prefix, 2016-12-08) we assert here in
cmd_submodule__helper() that we're not getting the flag unexpectedly.

1. 8c8195e (submodule--helper: introduce add-clone subcommand,
   2021-07-10)
2. 6e7c14e (submodule update --init: display correct path from
   submodule, 2017-01-06)
3. 1cf823d (submodule: remove unnecessary `prefix` based option
   logic, 2021-06-22)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>

builtin/submodule--helper.c

@@ -3377,15 +3377,15 @@ static struct cmd_struct commands[] = {
 	{"list", module_list, 0},
 	{"name", module_name, 0},
 	{"clone", module_clone, 0},
-	{"add", module_add, SUPPORT_SUPER_PREFIX},
+	{"add", module_add, 0},
 	{"update", module_update, 0},
 	{"resolve-relative-url-test", resolve_relative_url_test, 0},
 	{"foreach", module_foreach, SUPPORT_SUPER_PREFIX},
-	{"init", module_init, SUPPORT_SUPER_PREFIX},
+	{"init", module_init, 0},
 	{"status", module_status, SUPPORT_SUPER_PREFIX},
 	{"sync", module_sync, SUPPORT_SUPER_PREFIX},
 	{"deinit", module_deinit, 0},
-	{"summary", module_summary, SUPPORT_SUPER_PREFIX},
+	{"summary", module_summary, 0},
 	{"push-check", push_check, 0},
 	{"absorb-git-dirs", absorb_git_dirs, SUPPORT_SUPER_PREFIX},
 	{"is-active", is_active, 0},