bpo-30312: Small correction in datastructures set code sample (pythonGH-2081) (pythonGH-2085)

(cherry picked from commit ca81615)

Author: KatherineMichel

Doc/tutorial/datastructures.rst

@@ -466,7 +466,7 @@ Here is a brief demonstration::
    {'a', 'r', 'b', 'c', 'd'}
    >>> a - b                              # letters in a but not in b
    {'r', 'd', 'b'}
-   >>> a | b                              # letters in either a or b
+   >>> a | b                              # letters in a or b or both
    {'a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'}
    >>> a & b                              # letters in both a and b
    {'a', 'c'}