Use unicode scalar field characters instead of LaTeX

Co-authored-by: Daira Hopwood <daira@jacaranda.org>

zebra-chain/src/commitments/sapling.rs

@@ -17,11 +17,11 @@ use crate::{
     types::amount::{Amount, NonNegative},
 };
 
-/// Generates a random scalar from the scalar field \mathbb{F}_r_𝕁.
+/// Generates a random scalar from the scalar field 𝔽_{r_𝕁}.
 ///
 /// The prime order subgroup 𝕁^(r) is the order-r_𝕁 subgroup of 𝕁 after the
 /// Edwards cofactor h_𝕁 = 8 is factored out. This function is useful when
-/// generating the uniform distribution on \mathbb{F}_r_𝕁 needed for Sapling
+/// generating the uniform distribution on 𝔽_{r_𝕁} needed for Sapling
 /// commitment schemes' trapdoor generators.
 ///
 /// https://zips.z.cash/protocol/protocol.pdf#jubjub