[clang][Interp] Limit MaxBitInt to 128 bits

Looks like larger bitints aren't supported everywhere.

Author: tbaederr

clang/test/AST/Interp/intap.cpp

@@ -4,7 +4,7 @@
 // RUN: %clang_cc1 -std=c++20 -fms-extensions -verify=ref %s
 
 
-using MaxBitInt = _BitInt(8388608);
+using MaxBitInt = _BitInt(128);
 
 constexpr _BitInt(2) A = 0;
 constexpr _BitInt(2) B = A + 1;