tests/basics/class_getattr: Remove invalid test for __getattribute__.

Part of this test was trying to test some functionality of __getattribute__
but this method name was misspelt so it wasn't doing anything useful.
Fixing the typo in this name makes the test fail because MicroPython
doesn't support user defined __getattribute__ methods.  So this part of the
test is removed.  The remaining tests are modified slightly to make it
clearer what they are testing.

tests/basics/class_getattr.py

@@ -1,4 +1,4 @@
-# test that __getattr__, __getattrribute__ and instance members don't override builtins
+# test that __getattr__ and instance members don't override builtins
 class C:
     def __init__(self):
         self.__add__ = lambda: print('member __add__')
@@ -7,10 +7,8 @@ class C:
     def __getattr__(self, attr):
         print('__getattr__', attr)
         return None
-    def __getattrribute__(self, attr):
-        print('__getattrribute__', attr)
-        return None
 
 c = C()
-c.__add__
-c + 1 # should call __add__
+c.add # should call __getattr__
+c.__add__() # should load __add__ instance directly
+c + 1 # should call __add__ method directly