docs(overlays): clarify how to remove an overlay (#28989)

In https://github.com/ionic-team/ionic-framework/issues/28981 there was
some confusion surrounding how to remove an overlay from the DOM if it
was never presented. The `dismiss` method will remove the overlay from
the DOM, but only if the overlay is visible. Otherwise, it's a no-op.

This PR updates the `dismiss` method docs for each overlay component to
note that developers can use the browser's remove method to remove the
element from the DOM.

core/src/components/loading/loading.tsx

@@ -268,6 +268,10 @@ export class Loading implements ComponentInterface, OverlayInterface {
    * This can be useful in a button handler for determining which button was
    * clicked to dismiss the loading.
    * Some examples include: ``"cancel"`, `"destructive"`, "selected"`, and `"backdrop"`.
+   *
+   * This is a no-op if the overlay has not been presented yet. If you want
+   * to remove an overlay from the DOM that was never presented, use the
+   * [remove](https://developer.mozilla.org/en-US/docs/Web/API/Element/remove) method.
    */
   @Method()
   async dismiss(data?: any, role?: string): Promise<boolean> {