remove degrees_of_freedom methods

[strengejacke]

No description provided.

[strengejacke]

@vincentarelbundock I don't know if you call degrees_of_freedom() in one of your packages - it's now completely moved to insight::get_df(). From a user perspective, nothing should have changed. But since all methods were removed here and degrees_of_freedom() just calls insight::get_df() now, there may be new errors not detected yet.

My question: once this PR is merged, could you test your packages (I'm particularly thinking of modelsummary) with the GitHub version of parameters?

[strengejacke]

Oh, and of course the GitHub version of insight.

[vincentarelbundock]

Thanks for the heads-up. I think I had already moved everything to get_df(), so this should be no problem. I ran the test suite locally with Github versions of all easystats packages I depend on, and didn't seen any error.

Consolidation is a good move here. Well done!