Some Fuchsia zx tests failed from https://reviews.llvm.org/D153888:
https://turquoise-internal-review.git.corp.google.com/c/integration/+/729619
Use `ReservedMemoryDefault` for `SCUDO_FUCHSIA` to use the default
MemMap API, while test failures are debugged.
Differential Revision: https://reviews.llvm.org/D154538
using ReservedMemoryT = ReservedMemoryDefault;
using MemMapT = ReservedMemoryT::MemMapT;
#elif SCUDO_FUCHSIA
-using ReservedMemoryT = ReservedMemoryFuchsia;
+using ReservedMemoryT = ReservedMemoryDefault;
using MemMapT = ReservedMemoryT::MemMapT;
#elif SCUDO_TRUSTY
using ReservedMemoryT = ReservedMemoryDefault;