remote-ls: Don't show Locale/Debug and secondary arches by default.

Locale and Debug extensions, and refs for a secondary arch, when the
primary arch alternative exists, are not shown unless you specify
--all or -a.

This makes the default output more useful.

doc/flatpak-remote-ls.xml

@@ -118,6 +118,16 @@
                 </para></listitem>
             </varlistentry>
 
+            <varlistentry>
+                <term><option>--all</option></term>
+                <term><option>-a</option></term>
+
+                <listitem><para> Show everything. By default locale and
+                debug extensions as well as secondary arches when the primary
+                arch in available are hidden.
+                </para></listitem>
+            </varlistentry>
+
             <varlistentry>
                 <term><option>--updates</option></term>