blockdata: constants: Use wildcard import in unit tests

Import with wildcard is applicable in unit tests, use it.

src/blockdata/constants.rs

@@ -178,13 +178,13 @@ pub fn genesis_block(network: Network) -> Block {
 
 #[cfg(test)]
 mod test {
+    use super::*;
+
     use core::default::Default;
     use hashes::hex::FromHex;
 
     use network::constants::Network;
     use consensus::encode::serialize;
-    use blockdata::constants::{genesis_block, bitcoin_genesis_tx};
-    use blockdata::constants::{MAX_SEQUENCE, COIN_VALUE};
 
     #[test]
     fn bitcoin_genesis_first_transaction() {