T367115: Fix format removal bug

[medied]

https://phabricator.wikimedia.org/T367115

While working on #122, I noticed this bug on main when trying to fix the warning associated with the preview format removal feature. This seems to have been introduced in #116, where a change was made to use useRef to keep track of value changes. The fix presented here takes the best of the past solutions:

• Keep valueRef to keep track of previous value, but simplify as we don't really need lastValue state
• Favor handleTextFormatRemoval instead of removesPreviewFormat as the former is more robust
• This PR also actually fixes the warning that came with the previous solution

Please test carefully