Modify MSP-generated text indicating parent class in Proposition subclass pages

[mbrush]

At present, Proposition profile pages, e.g. here, contain MSP-generated text like this:

"Some VariantPathogenicityProposition attributes are inherited from ClinicalVariantProposition"

. . . which indicates an abstract ClinicalVariantProposition class in the model that was defined more as a mixin - to avoid having to repeat definitions of attributes that are inherited by several proposition subclasses.

On the 4-16-25 VA Call, @ahwagner agreed to modify MSP so that the indicated parent class in this text is the root Proposition class - with a reference that points to the Proposition page in the documentation.

The desired text and link for all Proposition profiles would then look as follows:

Some VariantPathogenicityProposition attributes are inherited from :ref:`Proposition`.

[mbrush]

@ahwagner @korikuzma This doesn't seem to have been addressed yet, and needs to be checked off the list of PRC requests. Any idea when you may get to it?

[korikuzma]

@ahwagner Let me know if you're tackling this or need me to

[ahwagner]

I am de-prioritizing this to post-1.0.