Fixed typo (#1705)

impl Finish for IResult Err::Incomplete panic message had a double-space

src/internal.rs

@@ -39,7 +39,7 @@ impl<I, O, E> Finish<I, O, E> for IResult<I, O, E> {
       Ok(res) => Ok(res),
       Err(Err::Error(e)) | Err(Err::Failure(e)) => Err(e),
       Err(Err::Incomplete(_)) => {
-        panic!("Cannot call `finish()` on `Err(Err::Incomplete(_))`: this result means that the parser does not have enough data to decide, you should gather more data and try to reapply  the parser instead")
+        panic!("Cannot call `finish()` on `Err(Err::Incomplete(_))`: this result means that the parser does not have enough data to decide, you should gather more data and try to reapply the parser instead")
       }
     }
   }