[REF] cleanup financial type form - remove complex inheritence

[eileenmcnaughton]

Overview

Minor cleanup - as with #16776

Before

Form inherits from CRM_Contribute_Form

After

Form inherits from CRM_Core_Form

Technical Details

Inheriting from 2 intermediary forms adds complexity with little benefit. Since we have the entityFormTrait
this increases use of that

Comments

[civibot]

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[colemanw]

Change makes sense. Tested it out on the demo site and form works as expected.