bpo-38605: Revert making 'from __future__ import annotations' the default (GH-25490)

This reverts commits 044a1048ca93d466965afc027b91a5a9eb9ce23c and 1be456ae9d53bb1cba2b24fc86175c282d1c2169, adapting the code to changes that happened after it.
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index 4d8198e..5f622b0 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -1018,6 +1018,14 @@
     Traceback (most recent call last):
     SyntaxError: cannot assign to __debug__
 
+    >>> def f(*args:(lambda __debug__:0)): pass
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to __debug__
+
+    >>> def f(**kwargs:(lambda __debug__:0)): pass
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to __debug__
+
     >>> with (lambda *:0): pass
     Traceback (most recent call last):
     SyntaxError: named arguments must follow bare *