fix: Multi choice options style regression (#1174)

## Launch Checklist


This PR fixes the silliness with the `maputnik-multibutton` requiring
`maputnik-button` and `@extend` not working because not included in said
file.

Fixes https://github.com/maplibre/maputnik/issues/1044

| Before | After |
|--------|--------|
|
![image](https://github.com/user-attachments/assets/0f4cd7a3-0359-4d0f-aaca-b346739cb760)
|
![image](https://github.com/user-attachments/assets/8b8f4aa4-b672-4495-9454-864d756799cc)
|


This also fixes the same issue a few lines up where
`maputnik-delete-filter` refers to an not imprted `@extend`.


 - [x] Write tests for all new functionality.
 - [x] Add an entry to `CHANGELOG.md` under the `## main` section.

src/styles/_filtereditor.scss

@@ -55,10 +55,6 @@
   margin-top: vars.$margin-3;
 }
 
-.maputnik-delete-filter {
-  @extend .maputnik-icon-button !optional; /* stylelint-disable-line */
-}
-
 .maputnik-filter-editor-block {
   display: flex;
   column-gap: 6px;
@@ -66,8 +62,6 @@
 }
 
 .maputnik-radio-as-button {
-  @extend .maputnik-button !optional; /* stylelint-disable-line */
-
   border: solid 1px transparent;
 
   &:focus-within {