gh-127238: adjust error message for sys.set_int_max_str_digits() (#127241)

Now it's correct and closer to Python/initconfig.c

Author: skirpichev

Misc/NEWS.d/next/Core_and_Builtins/2024-11-25-05-15-21.gh-issue-127238.O8wkH-.rst

@@ -0,0 +1 @@
+Correct error message for :func:`sys.set_int_max_str_digits`.

Python/sysmodule.c

@@ -4104,7 +4104,7 @@ _PySys_SetIntMaxStrDigits(int maxdigits)
 {
     if (maxdigits != 0 && maxdigits < _PY_LONG_MAX_STR_DIGITS_THRESHOLD) {
         PyErr_Format(
-            PyExc_ValueError, "maxdigits must be 0 or larger than %d",
+            PyExc_ValueError, "maxdigits must be >= %d or 0 for unlimited",
             _PY_LONG_MAX_STR_DIGITS_THRESHOLD);
         return -1;
     }