[libc++] Fix GDB pretty printer test on 32 bit targets

On 32 bit targets, size_t is unsigned int, not unsigned long, so
std::bitset's template argument gets printed with a `u` suffix,
not `ul`.
GitOrigin-RevId: 4d8db4a9970ec8cfc002f2a860df12c0c8c511bc
1 file changed