gbrief-2 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.

(cherry picked from commit c3c96a446b)

lib/layouts/g-brief2.layout

@@ -17,6 +17,9 @@ Sides			1
 PageStyle		Empty
 DefaultStyle		Standard
 
+# Babel is loaded internally
+Provides babel 1
+
 # This is just to show how to declare the default font.
 # The defaults are exactly those shown here.
 DefaultFont