gnu: Remove rust-rayon-1.1.

* gnu/packages/crates-io.scm (rust-rayon-1.1): Remove variable.
(rust-criterion-0.2, rust-gimli-0.18, rust-hashbrown-0.5,
rust-jpeg-decoder-0.1, rust-scroll-0.9, rust-syn-0.15)
[arguments]: Replace rust-rayon-1.1 with 1.3.