style: simplify destroyAll api due to private usage

src/modules/esl-mixin-element/ui/esl-mixin-registry.ts

@@ -170,15 +170,11 @@ export class ESLMixinRegistry {
     delete store[mixin];
   }
 
-  /**
-   * Destroys all mixins on the element
-   * @param el - host element to destroy all mixins
-   * @param deep - if true, will destroy all mixins on the subtree
-   */
-  private static destroyAll(el: HTMLElement, deep = true): void {
+  /** Destroys all mixins on the element and its subtree */
+  private static destroyAll(el: HTMLElement): void {
     const store = (el as any)[STORE] as Record<string, ESLMixinElement> | undefined;
     store && Object.keys(store).forEach((name) => ESLMixinRegistry.destroy(el, name));
-    if (!deep || !el.children || !el.children.length) return;
+    if (!el.children || !el.children.length) return;
     Array.prototype.forEach.call(el.children, (child: Element) => ESLMixinRegistry.destroyAll(child as HTMLElement));
   }
 }