Fix CI, NEWS updated

Author: efimov-mikhail

Include/internal/pycore_backoff.h

@@ -43,7 +43,7 @@ extern "C" {
 
 // We only use values x and backoffs b such that
 // x + 1 is near to 2**(2*b+1) and x + 1 is prime.
-static uint16_t value_and_backoff_next[] = {
+static const uint16_t value_and_backoff_next[] = {
     MAKE_VALUE_AND_BACKOFF(6, 1),
     MAKE_VALUE_AND_BACKOFF(30, 2),
     MAKE_VALUE_AND_BACKOFF(126, 3),

Misc/NEWS.d/next/Core_and_Builtins/2025-11-15-14-04-35.gh-issue-141589.VfdMDD.rst

@@ -1,2 +1,3 @@
-Change ``backoff counter`` to use powers of 4 instead of powers of 2.
+Change ``backoff counter`` to use prime numbers instead of powers of 2.
+Use only 3 bits for ``counter`` and 13 bits for ``value``.
 This allows to support values up to 8191. Patch by Mikhail Efimov.