Set 'height' instead of 'scale' for image in page header

The image is 67.3mm high, so the old scale 0.1 is approximaged by scaled height 6.5mm.

MLS.tex

@@ -16,7 +16,7 @@
 % needed for over-determined connectors (as it would otherwise overflow)
 \pagestyle{fancy}
 \rhead{Modelica Language Specification 3.5-dev\\ \nouppercase{\rightmark} \vspace{1mm}}
-\lhead{\includegraphics[scale=0.1]{Modelica_Language}}
+\lhead{\includegraphics[height=6.5mm]{Modelica_Language}}
 \renewcommand{\headrulewidth}{0.0pt}
 
 % Abstract