[TASK] Simplify modal callback handling

The fix from #84499 can be simplified a bit: class
"modal-content-loaded" is not needed with the callback
solution.

Resolves: #84559
Related: #84499
Releases: master
Change-Id: I2900ecafc06579076670f8678471530d03d0b63c
Reviewed-on: https://review.typo3.org/56477
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>

typo3/sysext/backend/Resources/Private/TypeScript/Modal.ts

@@ -343,25 +343,22 @@ class Modal {
     if (configuration.type === 'ajax') {
       const contentTarget = configuration.ajaxTarget ? configuration.ajaxTarget : Identifiers.body;
       const $loaderTarget = currentModal.find(contentTarget);
-      if (!$loaderTarget.hasClass('modal-content-loaded')) {
-        Icons.getIcon('spinner-circle', Icons.sizes.default, null, null, Icons.markupIdentifiers.inline).done((icon: string): void => {
-          $loaderTarget.html('<div class="modal-loading">' + icon + '</div>');
-          $.get(
-              <string>configuration.content,
-              (response: string): void => {
-                this.currentModal.find(contentTarget)
-                    .addClass('modal-content-loaded')
-                    .empty()
-                    .append(response);
-                if (configuration.ajaxCallback) {
-                  configuration.ajaxCallback();
-                }
-                this.currentModal.trigger('modal-loaded');
-              },
-              'html'
-          );
-        });
-      }
+      Icons.getIcon('spinner-circle', Icons.sizes.default, null, null, Icons.markupIdentifiers.inline).done((icon: string): void => {
+        $loaderTarget.html('<div class="modal-loading">' + icon + '</div>');
+        $.get(
+          <string>configuration.content,
+          (response: string): void => {
+            this.currentModal.find(contentTarget)
+              .empty()
+              .append(response);
+            if (configuration.ajaxCallback) {
+              configuration.ajaxCallback();
+            }
+            this.currentModal.trigger('modal-loaded');
+          },
+          'html'
+        );
+      });
     } else if (configuration.type === 'iframe') {
       currentModal.find(Identifiers.body).append(
         $('<iframe />', {