Update error message for type name

This change updates the error message in the `expect` call to display the correct message. If the `from_utf8` fails to unwrap it will be the result of _invalid_ utf8.

Author: bnbeckwith

git-object/src/types.rs

@@ -91,7 +91,7 @@ impl Kind {
 
 impl fmt::Display for Kind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(std::str::from_utf8(self.to_bytes()).expect("valid utf8 in kind name"))
+        f.write_str(std::str::from_utf8(self.to_bytes()).expect("invalid utf8 in kind name"))
     }
 }