Fix erroneous asserts.assert_count_equal docstring summary (#855)

Co-authored-by: Ang Li <angli@google.com>
diff --git a/mobly/asserts.py b/mobly/asserts.py
index e3fa007..70e1256 100644
--- a/mobly/asserts.py
+++ b/mobly/asserts.py
@@ -181,9 +181,9 @@
 
 
 def assert_count_equal(first, second, msg=None, extras=None):
-  """Asserts that two iterables have the same element count.
+  """Asserts that two iterables have the same elements, the same number of
+  times, without regard to order.
 
-  Element order does not matter.
   Similar to assert_equal(Counter(list(first)), Counter(list(second))).
 
   Args: