Remove unnecessary casts

Clippy emits a bunch of warnings of form:

 warning: casting to the same type is unnecessary ...

As suggested, remove the unnecessary casts.

bitcoin/src/bip152.rs

@@ -284,7 +284,7 @@ impl Decodable for BlockTransactionsRequest {
                 // Since the number of indices ultimately represent transactions,
                 // we can limit the number of indices to the maximum number of
                 // transactions that would be allowed in a vector.
-                let byte_size = (nb_indexes as usize)
+                let byte_size = (nb_indexes)
                     .checked_mul(mem::size_of::<Transaction>())
                     .ok_or(encode::Error::ParseFailed("Invalid length"))?;
                 if byte_size > encode::MAX_VEC_SIZE {

bitcoin/src/bip32.rs

@@ -627,7 +627,7 @@ impl ExtendedPrivKey {
                 Network::Testnet | Network::Signet | Network::Regtest => [0x04, 0x35, 0x83, 0x94],
             }[..],
         );
-        ret[4] = self.depth as u8;
+        ret[4] = self.depth;
         ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
         ret[9..13].copy_from_slice(&u32::from(self.child_number).to_be_bytes());
         ret[13..45].copy_from_slice(&self.chain_code[..]);
@@ -759,7 +759,7 @@ impl ExtendedPubKey {
                 Network::Testnet | Network::Signet | Network::Regtest => [0x04u8, 0x35, 0x87, 0xCF],
             }[..],
         );
-        ret[4] = self.depth as u8;
+        ret[4] = self.depth;
         ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
         ret[9..13].copy_from_slice(&u32::from(self.child_number).to_be_bytes());
         ret[13..45].copy_from_slice(&self.chain_code[..]);

bitcoin/src/blockdata/witness.rs

@@ -179,7 +179,7 @@ impl Witness {
 
     /// Returns the number of elements this witness holds
     pub fn len(&self) -> usize {
-        self.witness_elements as usize
+        self.witness_elements
     }
 
     /// Returns the bytes required when this Witness is consensus encoded

bitcoin/src/consensus/encode.rs

@@ -423,7 +423,7 @@ impl Encodable for VarInt {
             },
             _ => {
                 w.emit_u8(0xFF)?;
-                (self.0 as u64).consensus_encode(w)?;
+                self.0.consensus_encode(w)?;
                 Ok(9)
             },
         }

bitcoin/src/pow.rs

@@ -198,7 +198,7 @@ impl Target {
             size += 1;
         }
 
-        CompactTarget(compact | (size << 24) as u32)
+        CompactTarget(compact | (size << 24))
     }
 
     /// Returns true if block hash is less than or equal to this [`Target`].