LaTeX, beamer templates: Don't require 'float' package.

AS far as I can see, it isn't needed by anything pandoc does.

default.beamer

@@ -43,7 +43,6 @@ $if(verbatim-in-note)$
 $endif$
 $if(tables)$
 \usepackage{longtable}
-\usepackage{float} % provides the H option for float placement
 $endif$
 $if(url)$
 \usepackage{url}

default.latex

@@ -58,7 +58,6 @@ $if(verbatim-in-note)$
 $endif$
 $if(tables)$
 \usepackage{longtable}
-\usepackage{float} % provides the H option for float placement
 $endif$
 $if(graphics)$
 \usepackage{graphicx}