[core] fiber: increase fiber stack size (#46133)

Signed-off-by: hongchaodeng <[email protected]>

src/ray/core_worker/fiber.h

@@ -160,15 +160,7 @@ class FiberState {
   }
 
  private:
-  // The fiber stack size. 128 KiB on Linux and Windows. 256 KiB on Mac.
-  // Note that the default fiber stack size is 128 KiB. In the Mac CI environment, this is
-  // not large enough and thus it causes segfaults. See
-  // https://github.com/ray-project/ray/pull/44331.
-#if defined(__APPLE__)
   static constexpr size_t kStackSize = 1024 * 256;
-#else
-  static constexpr size_t kStackSize = 1024 * 128;
-#endif
 
   // The fiber stack allocator.
   boost::fibers::fixedsize_stack allocator_;