Drop isWindows/isMac from stable Processing API

(cherry picked from commit 7e80fc8)

Author: nyalldawson

python/plugins/processing/__init__.py

@@ -39,8 +39,6 @@
 qgis.processing.createAlgorithmDialog = createAlgorithmDialog
 qgis.processing.execAlgorithmDialog = execAlgorithmDialog
 qgis.processing.createContext = createContext
-qgis.processing.isWindows = isWindows
-qgis.processing.isMac = isMac
 
 
 def classFactory(iface):