fix typo

Author: sth4nth

chapter12/ppcaVb.m

@@ -5,7 +5,7 @@
 %   q: dimension of target space
 % Output:
 %   model: trained model structure
-%   ernergy: variantional lower bound
+%   L: variantional lower bound
 % Reference: 
 %   Pattern Recognition and Machine Learning by Christopher M. Bishop 
 % Written by Mo Chen ([email protected]).