gh-91687: modernize dataclass example typing (#103773)

modernize dataclass example typing `list` rather than `List` and comment as to that line being the alluded too error.

diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst
index 5f4dc25bfd7877199ff73a43bfab8cf40eb76abd..a04e5f744fa35039af8714f55675342e12936d0b 100644 (file)
--- a/Doc/library/dataclasses.rst
+++ b/Doc/library/dataclasses.rst
@@ -714,7 +714,7 @@ Using dataclasses, *if* this code was valid::
 
   @dataclass
   class D:
-      x: List = []
+      x: list = []      # This code raises ValueError
       def add(self, element):
           self.x += element