manifold/bin/cbc.py: fix typo

manifold/bin/cbc.py

@@ -440,7 +440,7 @@ output-png: test.png
 	ax.tick_params(axis='y', labelsize=12)
 	ax.grid(True)
 	canvas = FigureCanvas(fig)
-	fig.savefig(name+"_match_cummulative.png", bbox_inches='tight')
+	fig.savefig(name+"_match_cumulative.png", bbox_inches='tight')
 
 	fig = Figure()
 	ax = fig.add_subplot(111)