[3.9] bpo-42576: Clarify only debug builds are affected in news (GH-23663) (GH-23666)

(cherry picked from commit 6a7fb9d)


Co-authored-by: kj <[email protected]>

Automerge-Triggered-By: GH:gvanrossum

Author: miss-islington

Misc/NEWS.d/next/Core and Builtins/2020-12-05-22-34-47.bpo-42576.lEeEl7.rst

@@ -1,3 +1,4 @@
 ``types.GenericAlias`` will now raise a ``TypeError`` when attempting to
 initialize with a keyword argument.  Previously, this would cause the
-interpreter to crash.  Patch by Ken Jin.
+interpreter to crash if the interpreter was compiled with debug symbols.
+This does not affect interpreters compiled for release.  Patch by Ken Jin.