Inline text styles have minor display issues in editor

[laurelfulford]

Using the inline text styles cause some unexpected issue in the editor.

1. Create a new newsletter.
2. If not already, set your body and headers to different types of fonts: set one to serif and one to sans serif.
3. Add a Heading to your newsletter.
4. Use the inline text styles to give one word in your heading a different colour.
5. Note that the inline colour is not applied, but the word is now styled like your body font. In my case, the headings should be sans-serif, but using the inline text highlight made one word serif:

The culprit seems to be the mark tag that the inline styles use -- they're picking up this style in the editor instead of the heading font face:

.editor-styles-wrapper .block-editor-block-list__layout :not(code) {
  font-family: var(--newspack-body-font);
}

The inline colour options don't seem to be working because the has-primary-color styles aren't available in the header -- for other elements, the colours are applied inline.

Both of these styles appear to work as expected in the sent newsletter -- the header using the inline style all uses the correct font family, and the inline text is applied: