Update 01-parallel-programming.md

Author: csccva

intro-day/docs/01-parallel-programming.md

@@ -151,7 +151,7 @@ Simple domains with different computational cost
 
 <br>
 <!-- Copyright CSC -->
-![](img/mandelbrot-domains.png){.center width=50%}
+![](img/mandelbrot-domains.png){.center width=49%}
 </div>