Fix watcher selection dropdown being cut off

The watcher tab container was cutting of the dropdown because of
`overflow: auto` CSS requirements. The issue is fixed in this commit
by appending the dropdown to the body instead of as a direct child.

Closes https://community.openproject.org/projects/openproject/work_packages/43421/activity

frontend/src/app/features/work-packages/components/wp-single-view-tabs/watchers-tab/watchers-tab.html

@@ -17,11 +17,13 @@
     <div class="work-package--watchers-lookup hide-when-print"
          [hidden]="!allowedToAdd">
       <form name="watcherForm" novalidate>
-        <op-user-autocompleter [clearAfterSelection]="true"
+        <op-user-autocompleter
-                            (valueChange)="addWatcher($event)"
+          [clearAfterSelection]="true"
-                            [url]="availableWatchersPath"
+          (valueChange)="addWatcher($event)"
-                            class="wp-watcher--autocomplete">
+          [url]="availableWatchersPath"
-        </op-user-autocompleter>
+          appendTo="body"
+          class="wp-watcher--autocomplete"
+        ></op-user-autocompleter>
       </form>
     </div>
   </div>