primefield: remove shr support

It was noted as buggy in #1319.

Turns out it was completely unused, aside from fulfilling a bound in the
`elliptic-curve` crate, which has since been removed.

Closes #1319

Author: tarcieri

Cargo.lock

@@ -197,22 +197,6 @@ macro_rules! field_element_type {
 
                 res
             }
-
-            /// Right shifts the [`
-            #[doc = stringify!($fe)]
-            /// `].
-            pub const fn shr(&self, shift: u32) -> Self {
-                Self(self.0.wrapping_shr(shift))
-            }
-
-            /// Right shifts the [`
-            #[doc = stringify!($fe)]
-            /// `].
-            ///
-            /// Note: not constant-time with respect to the `shift` parameter.
-            pub const fn shr_vartime(&self, shift: u32) -> Self {
-                Self(self.0.wrapping_shr_vartime(shift))
-            }
         }
 
         impl $crate::ff::Field for $fe {
@@ -323,56 +307,6 @@ macro_rules! field_element_type {
             }
         }
 
-        impl ::core::ops::Shr<u32> for $fe {
-            type Output = Self;
-
-            #[inline]
-            fn shr(self, rhs: u32) -> Self {
-                Self::shr(&self, rhs)
-            }
-        }
-
-        impl ::core::ops::Shr<u32> for &$fe {
-            type Output = Self;
-
-            #[inline]
-            fn shr(self, rhs: u32) -> Self {
-                Self::shr(self, rhs)
-            }
-        }
-
-        impl ::core::ops::ShrAssign<u32> for $fe {
-            #[inline]
-            fn shr_assign(&mut self, rhs: u32) {
-                *self = Self::shr(self, rhs)
-            }
-        }
-
-        impl ::core::ops::Shr<usize> for $fe {
-            type Output = Self;
-
-            #[inline]
-            fn shr(self, rhs: usize) -> Self {
-                Self::shr(&self, rhs as u32)
-            }
-        }
-
-        impl ::core::ops::Shr<usize> for &$fe {
-            type Output = Self;
-
-            #[inline]
-            fn shr(self, rhs: usize) -> Self {
-                Self::shr(self, rhs as u32)
-            }
-        }
-
-        impl ::core::ops::ShrAssign<usize> for $fe {
-            #[inline]
-            fn shr_assign(&mut self, rhs: usize) {
-                *self = Self::shr(self, rhs as u32)
-            }
-        }
-
         impl ::core::fmt::Debug for $fe {
             fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 write!(f, "{}(0x{:X})", stringify!($fe), &self.0)