Renamed duplicate methods, and removed FileHandlingBudget class

src/main/java/no/ntnu/idatt1002/demo/data/Budget/GeneralBudget.java

@@ -112,7 +112,7 @@ public class GeneralBudget {
         }
     }
 
-    public void addToBudgetBudgetItem(double budgetAmount, String description, ExpenseCategory category) {
+    public void addToBudget(double budgetAmount, String description, ExpenseCategory category) {
         if ((totalSum() + budgetAmount) > maxAmount) {
             throw new IllegalArgumentException("Amount to be added goes over the max value of the budget");
         }