Update deprecations and removals

Author: BurntimeX

docs/migration/wsc61/deprecations_removals.md

@@ -29,6 +29,7 @@ With version 6.2, we have deprecated certain components and removed several othe
 - `wcf\system\tagging\ITagged` ([WoltLab/WCF#6291](https://github.com/WoltLab/WCF/pull/6291))
 - `wcf\system\moderation\AbstractDeletedContentProvider` ([WoltLab/WCF#6285](https://github.com/WoltLab/WCF/pull/6285))
 - `wcf\system\moderation\IDeletedContentProvider` ([WoltLab/WCF#6285](https://github.com/WoltLab/WCF/pull/6285))
+- `wcf\system\form\builder\field\MultipleSelectFormField`
 
 #### Methods