`on` mixin handler runs twice in "nested" `clientEntry` components

Reproduction steps

1. Run https://github.com/okalil/remix-3-beta-bugs/tree/main/on-mixin-runs-twice
2. Click the first button, see 'click' logged once.
3. Click the second button, see 'click' logged twice.

Expected behavior

On click the second button 'click' is also logged once.

Actual behavior

On click the second button 'click' is logged twice.