fix: Change to compile for wasm32-unknown-unknown target

[morenol]

Right now if we run

cargo build --target wasm32-unknown-unknown --release --all-features it fails with:

error[E0308]: mismatched types
  --> src/dataset/mod.rs:88:49
   |
88 |         let num_features = usize::from_le_bytes(buffer);
   |                                                 ^^^^^^ expected an array with a fixed size of 4 elements, found one with 8 elements

error[E0308]: mismatched types
  --> src/dataset/mod.rs:90:48
   |
90 |         let num_samples = usize::from_le_bytes(buffer);
   |                                                ^^^^^^ expected an array with a fixed size of 4 elements, found one with 8 elements

error: aborting due to 2 previous errors

According to the documentation from_le_bytes takes an array of length 2, 4 or 8 bytes depending on the target pointer size.