gh-119311: Add missing magic number (3571) for 3.13.0b1 (#125771)

Add missing magic number 3571 for 3.13b1

It was added after branching in 6394a72#diff-efefe383b3a81d16150c280db0b64eed7569254299418f64cc0d749f8e16f3a4R475

Author: frenzymadness

Include/internal/pycore_magic_number.h

@@ -251,6 +251,7 @@ Known values:
     Python 3.13a1 3568 (Change semantics of END_FOR)
     Python 3.13a5 3569 (Specialize CONTAINS_OP)
     Python 3.13a6 3570 (Add __firstlineno__ class attribute)
+    Python 3.13b1 3571 (Fix miscompilation of private names in generic classes)
     Python 3.14a1 3600 (Add LOAD_COMMON_CONSTANT)
     Python 3.14a1 3601 (Fix miscompilation of private names in generic classes)
     Python 3.14a1 3602 (Add LOAD_SPECIAL. Remove BEFORE_WITH and BEFORE_ASYNC_WITH)