remove duplicated check in falcon verification

Minor change removing a duplicated check of `h_digest==pubkey_com`at
`src/dsa/rpo_falcon512/signature.rs#L100`, which is already done at
`src/dsa/rpo_falcon512/signature.rs#L95`.

src/dsa/rpo_falcon512/signature.rs

@@ -97,7 +97,7 @@ impl Signature {
         }
 
         let c = hash_to_point_rpo256(message, &self.nonce);
-        h_digest == pubkey_com && verify_helper(&c, &self.s2, self.pk_poly())
+        verify_helper(&c, &self.s2, self.pk_poly())
     }
 }