remove CKEditor 4 (contrib) and Convert Entity Media Embed

Now that we've switched to CK5 we can remove the contrib module for CK4. At this time, we should be safe to remove the Convert Entity Media Embed module as well.

patches/set_viewmode_to_string.patch

+diff --git a/core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Media.php b/core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Media.php
+index c6b9f345a9..9b6031da03 100644
+--- a/core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Media.php
++++ b/core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Media.php
+@@ -115,12 +115,13 @@ private function configureViewModes(EditorInterface $editor) {
+       if (array_key_exists($view_mode, $bundles_per_view_mode)) {
+         $specific_bundles = $bundles_per_view_mode[$view_mode];
+         if ($view_mode == $default_view_mode) {
++          $view_mode_str = strval($view_mode);
+           $element_style_configuration[] = [
+             'isDefault' => TRUE,
+             'name' => $default_view_mode,
+             'title' => $all_view_modes[$view_mode],
+             'attributeName' => 'data-view-mode',
+-            'attributeValue' => $view_mode,
++            'attributeValue' => $view_mode_str,
+             'modelElements' => ['drupalMedia'],
+             'modelAttributes' => [
+               'drupalMediaType' => array_keys($media_bundles),
+@@ -128,11 +129,12 @@ private function configureViewModes(EditorInterface $editor) {
+           ];
+         }
+         else {
++          $view_mode_str = strval($view_mode);
+           $element_style_configuration[] = [
+             'name' => $view_mode,
+             'title' => $all_view_modes[$view_mode],
+             'attributeName' => 'data-view-mode',
+-            'attributeValue' => $view_mode,
++            'attributeValue' => $view_mode_str,
+             'modelElements' => ['drupalMedia'],
+             'modelAttributes' => [
+               'drupalMediaType' => $specific_bundles,