Improve the grammar of a non-sentence.

Doc/library/queue.rst

@@ -20,8 +20,8 @@ module implements all the required locking semantics.  It depends on the
 availability of thread support in Python; see the :mod:`threading`
 module.
 
-Implements three types of queue whose only difference is the order that
-the entries are retrieved.  In a FIFO queue, the first tasks added are
+The module implements three types of queue, which differ only in the order in
+which the entries are retrieved.  In a FIFO queue, the first tasks added are
 the first retrieved. In a LIFO queue, the most recently added entry is
 the first retrieved (operating like a stack).  With a priority queue,
 the entries are kept sorted (using the :mod:`heapq` module) and the