fixed a comment

Author: habibasorour

source/ch6_definingclasses.ptx

@@ -839,7 +839,8 @@ class Student:
     def __init__(self, id, name): 
         self.id = id
         self.name = name
-        Student.numStudents = Student.numStudents + 1 # this is a static variable, that can be accessed without the self prefix
+        # this is a static variable, that can be accessed without the self prefix
+        Student.numStudents = Student.numStudents + 1 
 def main():
     for i in range(10):
         s = Student(i,"Student-"+str(i)) # create a new Student object