Validator Warning: Remove AccountProviderType

AccountProviderType was deprecated in AccountService.v1_5_0.
The latest AccountService is 1.7.0. Move from 1.4.0 to 1.5.0.

Fixes validator warnings:
WARNING - LDAP.AccountProviderType: The given property is deprecated
by revision: This property is deprecated because the account provider
type is known when used in the LDAP and ActiveDirectory objects.

WARNING - ActiveDirectory.AccountProviderType: The given property is
deprecated by revision: This property is deprecated because the
account provider type is known when used in the LDAP and
ActiveDirectory objects.

Although not sure if the validator should have thrown a
warning since the version of AccountService in bmcweb still
allowed this property.

AccountProviderType is not used in the GUI or other places.

Resolves openbmc/bmcweb#118

Tested: Passed validator.
Change-Id: Ifa15cdd2dfd0d740e42add778f30d00e7885ed4b
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>