Docs: Update SyntaxError message in REPL example for list comprehension (pythonGH-93901)

Author: csabella

Doc/tutorial/datastructures.rst

@@ -268,10 +268,10 @@ it must be parenthesized. ::
    [(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]
    >>> # the tuple must be parenthesized, otherwise an error is raised
    >>> [x, x**2 for x in range(6)]
-     File "<stdin>", line 1, in <module>
+     File "<stdin>", line 1
        [x, x**2 for x in range(6)]
-                  ^
-   SyntaxError: invalid syntax
+        ^^^^^^^
+   SyntaxError: did you forget parentheses around the comprehension target?
    >>> # flatten a list using a listcomp with two 'for'
    >>> vec = [[1,2,3], [4,5,6], [7,8,9]]
    >>> [num for elem in vec for num in elem]