Sync FuchsiaConfig with downstream's custom_scudo_config.h (#89244)

Downstream disabled EnableContiguousRegions on RISCV-64 to avoid
running out of virtual memory, but our tests still use the internal
FuchsiaConfig class, which therefore needs to be changed too.

GitOrigin-RevId: adc11b34b1d7f99b3931f945073a652f0dec5aaf
1 file changed