Remove editor custom elements

[spelkey-ucd]

when doing the initial build, we inserted lit custom elements into the editor in order to make the transition to React a bit easier. IMHO, this has ended up causing more problems than it has solved. Now, with the new section block, this is especially evident since a lot of colors are not rendering correctly due to the shadowdom. So, we could either:

1. disable the shadow dom
2. remove the offending lit components and use the native wordpress richtext component instead

I think the latter is a better long-term solution since, if the past is any indication, Lit/React compatibility issues will continue to be an issue.