Rollup merge of #44559 - frewsxcv:frewsxcv-rm-loop, r=sfackler

Remove unneeded `loop`.

None

src/liballoc/btree/set.rs

@@ -1110,15 +1110,13 @@ impl<'a, T: Ord> Iterator for Union<'a, T> {
     type Item = &'a T;
 
     fn next(&mut self) -> Option<&'a T> {
-        loop {
         match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
-                Less => return self.a.next(),
+            Less => self.a.next(),
             Equal => {
                 self.b.next();
-                    return self.a.next();
+                self.a.next()
-                }
-                Greater => return self.b.next(),
             }
+            Greater => self.b.next(),
         }
     }