Fix stable(since) attribute for BTreeMap::remove_entry

Author: jplatte

src/liballoc/collections/btree/map.rs

@@ -930,7 +930,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
     /// assert_eq!(map.remove_entry(&1), None);
     /// ```
-    #[stable(feature = "btreemap_remove_entry", since = "1.44.0")]
+    #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
     pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
     where
         K: Borrow<Q>,