pkstrings: Use converted PKString result in Display

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

pkstrings/src/pkstring.rs

@@ -136,7 +136,7 @@ impl Deref for PKString {
 
 impl fmt::Display for PKString {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", &self.0)
+        write!(f, "{:?}", String::from(self))
     }
 }