Fix clippy - #264

warning: unexpected `cfg` condition value: `parallel`
   --> bitvm/src/bn254/ell_coeffs.rs:329:21
    |
329 |         let mut f = cfg_chunks_mut!(pairs, 4)
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: expected values for `feature` are: `fuzzing`
    = note: using a cfg inside a macro will use the cfgs from the destination crate and not the ones from the defining crate
    = help: try referring to `cfg_chunks_mut` crate for guidance on how handle this unexpected cfg
    = help: the macro `cfg_chunks_mut` may come from an old version of the `ark_std` crate, try updating your dependency with `cargo update -p ark_std`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default
    = note: this warning originates in the macro `cfg_chunks_mut` (in Nightly builds, run with -Z macro-backtrace for more info)