Stabilize 'entry_and_modify' feature for BTreeMap

Author: hedgehog1024

src/liballoc/btree/map.rs

@@ -2114,7 +2114,6 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(entry_and_modify)]
     /// use std::collections::BTreeMap;
     ///
     /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
@@ -2129,7 +2128,7 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
     ///    .or_insert(42);
     /// assert_eq!(map["poneyland"], 43);
     /// ```
-    #[unstable(feature = "entry_and_modify", issue = "44733")]
+    #[stable(feature = "entry_and_modify", since = "1.25.0")]
     pub fn and_modify<F>(self, mut f: F) -> Self
         where F: FnMut(&mut V)
     {