[BUGFIX] Respect data-content for modals again

With the upgrade to Bootstrap 5, modals unintentionally don't support
the `data-content` attribute anymore as this was automatically migrated
to the namespaced variant `data-bs-content`. While this is technically
correct for Bootstrap 5, Core still needs to support the old variant as
documented.

Resolves: #98067
Releases: main, 12.4, 11.5
Change-Id: I544cbd779c808727c472575654adca3dc4c91197
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79961
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

Build/Sources/TypeScript/backend/Resources/Public/TypeScript/Modal.ts

@@ -377,7 +377,7 @@ class Modal {
     $(theDocument).on('click', '.t3js-modal-trigger', (evt: JQueryEventObject): void => {
       evt.preventDefault();
       const $element = $(evt.currentTarget);
-      const content = $element.data('bs-content') || 'Are you sure?';
+      const content = $element.data('bs-content') || $element.data('content') || 'Are you sure?';
       let severity = SeverityEnum.info;
       if ($element.data('severity') in SeverityEnum) {
         const severityKey: keyof typeof SeverityEnum = $element.data('severity');