Remove unnecessary self:: from error import

`Error` is in this file, no need for `self::Error`.

bitcoin/src/address/error.rs

@@ -86,7 +86,7 @@ impl fmt::Display for Error {
 #[cfg(feature = "std")]
 impl std::error::Error for Error {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        use self::Error::*;
+        use Error::*;
 
         match self {
             Base58(e) => Some(e),