Remove Iterator::size_hint() implementation

I'm not sure why the author added this in the first place, but I bet we
don't need this.

So remove code we do not need. Feel free to prove me wrong and revert
this patch.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

lib/core/libimagerror/src/iter.rs

@@ -48,12 +48,6 @@ impl<I, F, T> Iterator for UnwrapWith<I, F>
             }
         }
     }
-
-    #[inline]
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let (_, upper) = self.iter.size_hint();
-        (0, upper)
-    }
 }