updating to rust-bitcoin 0.27

Author: sandipndev

json/Cargo.toml

@@ -21,4 +21,4 @@ path = "src/lib.rs"
 serde = { version = "1", features = [ "derive" ] }
 serde_json = "1"
 
-bitcoin = { version = "0.26", features = [ "use-serde" ] }
+bitcoin = { version = "0.27", features = [ "use-serde" ] }