apparmor: Fix smatch warning in aa_remove_profiles

smatch reports
  error: potential NULL dereference 'ns'.

this can not actually occur because it relies on aa_split_fqname setting
both ns_name and name as null but ns_name will actually always have a
value in this case.

so remove the unnecessary if (ns_name) conditional that is resulting
in the false positive further down.

Signed-off-by: John Johansen <john.johansen@canonical.com>