Update and rename MultiTouchHelper to multiTouchHelper.py

不知道能不能用，有没有大佬帮忙测试一下，不能用就退回来删了。。按照java的改成python

uiautomator2/MultiTouchHelper → uiautomator2/multiTouchHelper.py

@@ -3,7 +3,7 @@
 from uiautomator2 import PointerInput, Sequence, Pause
 from typing import List
 
-class MultiTouchHelper:
+class multiTouchHelper:
     def __init__(self, device: Device):
         self.device = device