s4/dsdb/pytest/ldap_schema: remove duplicate test

s4/dsdb/pytest/ldap_schema: remove duplicate test

The tests differ in two lines, thus:

     def test_subClassOf(self):
     -        """ Testing usage of custom child schamaClass
     +        """ Testing usage of custom child classSchema

[...]

   -governsId: 1.3.6.1.4.1.7165.4.6.2.6.3.""" + str(random.randint(1, 100000)) + """
   +governsId: 1.3.6.1.4.1.7165.4.6.2.6.7.""" + str(random.randint(1, 100000)) + """

with the governsId OID changed because it was noticed they were colliding.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Noel Power <npower@samba.org>