Sand block shading is now too light

In the 1.21.50.24 Preview, Sand blocks had darker shading consistent with the Java Edition. However, in the 1.21.50.25 Preview, the shading appears much lighter, negatively impacting the look of Desert biomes and breaking parity with the Java Edition.

The fix is straightforward: in blocks.json, change the ambient_occlusion_exponent value for Sand blocks from 0.55 to 1.0.

Repro Steps:

1. Travel to a Desert biome in the 1.21.50.24 Preview.
2. Observe the shading on Sand blocks.
3. Travel to a Desert biome in the 1.21.50.25 Preview.
4. Note the difference in shading on Sand blocks.

Expected Results:
Sand blocks should have darker, consistent shading, aligned with the Java Edition.

Actual Results:
In the 1.21.50.25 Preview, Sand blocks have noticeably lighter shading.