fix(richtext-lexical): hover style of the button to remove blocks (#8154)

## Description

Fix #8045

Before: hover with same color as background, as in the issue
description.

After (light):
![Screenshot 2024-09-10 at 9 36
21 AM](https://github.com/user-attachments/assets/260dbc69-a583-42f6-9b25-a81b8d8d4f70)

After (dark):
![Screenshot 2024-09-10 at 9 35
34 AM](https://github.com/user-attachments/assets/3606ee3c-24d6-43dd-8a0e-11d12e1fe779)


- [x] I have read and understand the
[CONTRIBUTING.md](https://github.com/payloadcms/payload/blob/main/CONTRIBUTING.md)
document in this repository.

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## Checklist:

- [x] Existing test suite passes locally with my changes
- [x] I have made corresponding changes to the documentation

Author: GermanJablo

packages/richtext-lexical/src/features/blocks/client/component/index.scss

@@ -81,6 +81,9 @@
 
   &__removeButton.btn {
     margin: 0;
+    &:hover {
+      background-color: var(--theme-elevation-200);
+    }
   }
 
   &__block-header {