Fix .this to .self in python example (RefactoringGuru#111)

Author: mdczaplicki

simple/python/replace-parameter-with-method-call_before.py

@@ -1,4 +1,4 @@
 basePrice = quantity * itemPrice
-seasonalDiscount = this.getSeasonalDiscount()
-fees = this.getFees()
-finalPrice = discountedPrice(basePrice, seasonalDiscount, fees)
+seasonalDiscount = self.getSeasonalDiscount()
+fees = self.getFees()
+finalPrice = discountedPrice(basePrice, seasonalDiscount, fees)