Bug 1159255 - Remove MSVC_ENABLE_PGO from moz.build. r=aleth

mailnews/intl/moz.build

@@ -30,8 +30,6 @@ charsetalias = GENERATED_FILES['charsetalias.properties.h']
 charsetalias.script = TOPSRCDIR + '/mozilla/intl/locale/props2arrays.py'
 charsetalias.inputs = ['charsetalias.properties']
 
-MSVC_ENABLE_PGO = True
-
 FINAL_LIBRARY = 'mail'
 
 # Tests need more attention before they can be enabled.