Fix using Beamer with geometry (#5505)

Beamer already loads geometry, so we need to use the `\geometry`
command to set geometry options.

data/templates/default.latex

@@ -229,8 +229,12 @@ $if(verbatim-in-note)$
 \VerbatimFootnotes % allow verbatim text in footnotes
 $endif$
 $if(geometry)$
+$if(beamer)$
+\geometry{$for(geometry)$$geometry$$sep$,$endfor$}
+$else$
 \usepackage[$for(geometry)$$geometry$$sep$,$endfor$]{geometry}
 $endif$
+$endif$
 $if(beamer)$
 \newif\ifbibliography
 $endif$