Fix LaTeX formatting for function (\left...\right)

Corrected the formatting of a piecewise function in LaTeX.

Author: baumbude

paper/paper.md

@@ -78,10 +78,10 @@ Single dollars ($) are required for inline mathematics e.g. $f(x) = e^{\pi/x}$
 
 Double dollars make self-standing equations:
 
-$$\Theta(x) = \left\{\begin{array}{l}
+$$\Theta(x) = \left(\begin{array}{l}
 0\textrm{ if } x < 0\cr
 1\textrm{ else}
-\end{array}\right.$$
+\end{array}\right).$$
 
 You can also use plain \LaTeX for equations
 \begin{equation}\label{eq:fourier}