rustfmt is wrong on this one but whatever

rustfmt is wrong that f()? should be preferred over f() ?, as errors paths should often be highlighted, but nobody merged that fix yet, so whatever. 
rust-lang/rustfmt#5595

ec/src/hashing/map_to_curve_hasher.rs

@@ -33,7 +33,7 @@ where
 {
     fn new(domain: &[u8]) -> Result<Self, HashToCurveError> {
         #[cfg(test)]
-        M2C::check_parameters() ?;
+        M2C::check_parameters()?;
         Ok(MapToCurveBasedHasher {
             field_hasher: H2F::new(domain),
             _curve_mapper: PhantomData,