[3.12] gh-121130: Fix f-string format specifiers with debug expressions (GH-121150) (#122063)

Author: pablogsal

Doc/library/ast.rst

@@ -302,9 +302,7 @@ Literals
                                 Name(id='a', ctx=Load())],
                             keywords=[]),
                         conversion=-1,
-                        format_spec=JoinedStr(
-                            values=[
-                                Constant(value='.3')]))]))
+                        format_spec=Constant(value='.3'))]))
 
 
 .. class:: List(elts, ctx)