apparmor: Fix one kernel-doc comment

Fix one kernel-doc comment to silence the warnings:
security/apparmor/domain.c:46: warning: Function parameter or member 'to_cred' not described in 'may_change_ptraced_domain'
security/apparmor/domain.c:46: warning: Excess function parameter 'cred' description in 'may_change_ptraced_domain'

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=7036


Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>