[3.14] gh-135110: Fix misleading `generator.close()` documentation (GH-135152) (GH-135985)

gh-135110: Fix misleading `generator.close()` documentation (GH-135152)

The documentation incorrectly stated that generator.close() 'raises' a
GeneratorExit exception. This was misleading because the method doesn't
raise the exception to the caller - it sends the exception internally
to the generator and returns None.
(cherry picked from commit 0d76dccc3b4376ba075a1737f58809e3d83aaaa3)

Co-authored-by: Connor Denihan <188690869+cdenihan@users.noreply.github.com>