End of Internet Explorer 11 support

The following pages are not working properly anymore with this browser:
- manage_config_workflow_page.php (since 2.22.0)
- account_prefs_inc.php (since 2.25.0)

This makes the end of support official, by removing IE 11 from the list
of supported browsers in Admin Guide's Client Requirements section.

Fixes #29198

docbook/Admin_Guide/en-US/Installation.xml

@@ -373,12 +373,17 @@
 
 			<itemizedlist>
 				<listitem><para>Firefox</para></listitem>
-				<listitem><para>Internet Explorer 11</para></listitem>
 				<listitem><para>Edge</para></listitem>
 				<listitem><para>Chrome</para></listitem>
 				<listitem><para>Safari</para></listitem>
 				<listitem><para>Opera</para></listitem>
 			</itemizedlist>
+
+			<note>
+				<para>Support for <emphasis>Internet Explorer 11</emphasis>
+					ended with release 2.22.0.
+				</para>
+			</note>
 		</section>
 	</section>