fix(editor): clear selection after toggle latex editor (#12637)

- **fix(editor): clear selection after toggle latex editor**
- **chore: remove useless test**

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - LaTeX rendering now outputs MathML format for improved accessibility and compatibility.
  - Added support for KaTeX styling to enhance LaTeX display in the playground.

- **Bug Fixes**
  - Improved editor behavior by resetting the selection group before opening the LaTeX editor.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/inlines/latex/src/latex-node/latex-node.ts

@@ -188,6 +188,8 @@ export class AffineLatexNode extends SignalWatcher(
     this._editorAbortController?.abort();
     this._editorAbortController = new AbortController();
 
+    blockComponent.selection.setGroup('note', []);
+
     const portal = createLitPortal({
       template: html`<latex-editor-menu
         .std=${this.std}