gh-141044: Update NEWS for TSan 12-margin stack_size floor

Author: KingLizard1020

Misc/NEWS.d/next/Library/2026-09-14-20-45-00.gh-issue-141044.Ks8nQm.rst

@@ -1,7 +1,8 @@
 Fix a reference leak when creating a :class:`threading.Thread` after
 setting a small custom stack size with :func:`threading.stack_size` in
 debug and sanitizer builds. Those builds need extra C stack, so
-:func:`!_thread.stack_size` now requires 6 stack margins (as ThreadSanitizer
-already did). Sizes that previously appeared to work (for example 127 KiB
-on 64-bit debug/ASan builds) now raise :exc:`ValueError`. Release builds
-are unchanged. Patch by Kailash Nelson.
+:func:`!_thread.stack_size` now requires 6 stack margins on debug/ASan/UBSan
+builds and 12 on ThreadSanitizer builds (which only use half the stack).
+Sizes that previously appeared to work (for example 127 KiB on 64-bit
+debug/ASan builds) now raise :exc:`ValueError`. Release builds are
+unchanged. Patch by Kailash Nelson.