Behavior change of { MentionsInput when replacing existing tokens

[six7]

2.0 changed something on behavior when it comes to replacing parts of a token reference with something that the user picks from the { mentions input.

Expected: The token reference as a whole is replaced. Actual: We insert double curly brackets and force the user to replace it manually

We should fix this behavior with an upgrade to our custom solution of a MentionsInput instead of relying on rc-mentions which produces this behavior AFAIK.

https://github.com/tokens-studio/figma-plugin/assets/4548309/86621eb3-0ed3-460f-a8ec-e6cbb6f611fc