[std] Remove unused package 'xspace'

Fixes #1433.

Author: jensmaurer

source/std.tex

@@ -27,7 +27,6 @@
 \usepackage{mathrsfs}     % mathscr font
 \usepackage[final]{microtype}
 \usepackage{multicol}
-\usepackage{xspace}
 \usepackage{lmodern}
 \usepackage[T1]{fontenc}
 \usepackage[pdftex, final]{graphicx}