Remove custom hash derives to fix build errors

The upstream impl_array_newtype now implements a core::hash::Hash. This
caused a breaking changed here :( despite it being a minor release.

Author: sanket1729

secp256k1-zkp-sys/src/zkp.rs

@@ -490,12 +490,6 @@ impl Default for Tag {
     }
 }
 
-impl hash::Hash for Tag {
-    fn hash<H: hash::Hasher>(&self, state: &mut H) {
-        self.0.hash(state)
-    }
-}
-
 impl From<[u8; 32]> for Tag {
     fn from(bytes: [u8; 32]) -> Self {
         Tag(bytes)
@@ -526,12 +520,6 @@ impl Default for PedersenCommitment {
     }
 }
 
-impl hash::Hash for PedersenCommitment {
-    fn hash<H: hash::Hasher>(&self, state: &mut H) {
-        state.write(&self.0)
-    }
-}
-
 /// A ring signature for the "whitelist" scheme.
 #[repr(C)]
 #[derive(Clone)]

src/zkp/generator.rs

@@ -8,7 +8,7 @@ use {constants, from_hex, Error, Secp256k1, Signing, Tag};
 ///
 /// Contrary to a [`crate::SecretKey`], the value 0 is also a valid tweak.
 /// Values outside secp curve order are invalid tweaks.
-#[derive(Default, Hash)]
+#[derive(Default)]
 pub struct Tweak([u8; constants::SECRET_KEY_SIZE]);
 impl_array_newtype!(Tweak, u8, constants::SECRET_KEY_SIZE);