Hide Gtk.Button because the GNOME Software Developmen Kit on Flathub is
only available for Linux.

--- src/manuals-window.ui.orig	2025-09-13 00:58:35 UTC
+++ src/manuals-window.ui
@@ -131,6 +131,7 @@ Or, press Ctrl+W to close the window</property>
                             <property name="action-name">win.show-bundle-dialog</property>
                             <property name="label" translatable="yes">Install Documentation…</property>
                             <property name="halign">center</property>
+                            <property name="visible">false</property>
                             <style>
                               <class name="pill"/>
                             </style>