Don't show keyboard layout flags by default

In the past we only supported layouts, now we also support
input modes.

Say you're using ibus/mozc for Japanese. We don't just show JP,
we show a hiragana or katakana or A symbol depending on the input mode.

Flags can't really show that, so that leads to a mixture of flags
and symbols for some users. The best OOTB experience is thus to not
use flags here.

Author: mtwebster

schemas/org.cinnamon.desktop.interface.gschema.xml.in

@@ -279,7 +279,7 @@
       <summary>Enable or disable gtk overlay scrollbars</summary>
     </key>
     <key name="keyboard-layout-show-flags" type="b">
-      <default>true</default>
+      <default>false</default>
       <summary>Prefer country flags to group names when showing keyboard layouts.</summary>
     </key>
     <key name="keyboard-layout-use-upper" type="b">