Update library/core/src/iter/adapters/dedup.rs

Co-authored-by: Cameron Steffen <cam.steffen94@gmail.com>

Author: slerpyyy

library/core/src/iter/adapters/dedup.rs

@@ -149,8 +149,8 @@ where
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let min = self.last.as_ref().map(|_| 1).unwrap_or(0);
-        let max = self.inner.size_hint().1;
+        let min = matches!(self.last, Some(Some(_))).into();
+        let max = self.inner.size_hint().1.map(|max| max + min);
         (min, max)
     }
 }