Cleanup: Remove wyrm specific icon sass

[Blendify]

This removes wyrm specific icon sass and migrates fully to using font awesome.

There should be no difference to users

[stsewd]

I guess this can be updated and merged after https://github.com/readthedocs/sphinx_rtd_theme/pull/1064/files

[Blendify]

This pull requests should actually be merged first, I based #1064 on the changes here.

[Blendify]

I guess the question is if we want to wait for a larger release or not

[stsewd]

Got it, I think we should include this together with the other in the same release

[Blendify]

@agjohnson is this change acceptable outside of the wyrm/bootstrap/sphinx2/html4/fontawesome5 changes?

[agjohnson]

I don't think we need to be too careful here, but removing classes that downstream users might have been using should at very least be a breaking change probably.

[agjohnson]

I maybe have slight concern here about removing the class, in case anyone downstream is using the .icon classes. This might be another backwards incompatible change

[agjohnson]

I'll target a 1.1 release for now, however I think this probably makes sense in a 2.0 release with a few other backwards incompatible changes before a 3.0 or greater bootstrap release.

[Blendify]

@agjohnson can this go into 1.1?

[benjaoming]

Great update, should be merged quickly once we start working on 2.0. We could write alias css classes for .icon-* for backwards compatibility and add a deprecation note in the changelog.