Remove XXX comments.

Author: serhiy-storchaka

Lib/test/test_memoryio.py

@@ -487,15 +487,11 @@ def test_getbuffer_gc_collect(self):
         # Create a reference loop.
         a = [buf]
         a.append(a)
-        # XXX The following code is not obvious because the current behaviour
-        # is not normal;
         # The Python implementation emits an unraisable exception.
         with support.catch_unraisable_exception():
             del memio
         del buf
         del a
-        # XXX The following code is not obvious because the current behaviour
-        # is not normal;
         # The C implementation emits an unraisable exception.
         with support.catch_unraisable_exception():
             gc.collect()