g-brief loads babel internally. So don't load it ourselves.

This makes the class fully functional with non-TeX fonts (it uses
\babelfont for the purpose). Before, docs were compiling but the
output was wrong.

lib/layouts/g-brief.layout

@@ -18,6 +18,9 @@ Sides                   1
 PageStyle               Empty
 DefaultStyle            Letter
 
+# Babel is loaded internally
+Provides babel 1
+
 
 Style Letter
 	Margin                Static