exec: Delete unnecessary statements in remove_arg_zero()

'ret=0; ' In actual operation, the ret was not modified, so this
sentence can be removed.

Signed-off-by: Li kunyu <kunyu@nfschina.com>
Link: https://lore.kernel.org/r/20240220052426.62018-1-kunyu@nfschina.com
Signed-off-by: Kees Cook <keescook@chromium.org>