Rollup merge of rust-lang#73667 - nrabulinski:master, r=Dylan-DPC

Update BTreeMap::new() doc

Updates the documentation according to [this comment](https://github.com/rust-lang/rust/pull/72876/files/0c5c644c91edf6ed949cfa5ffc524f43369df604#r433232581) on rust-lang#72876

src/liballoc/collections/btree/map.rs

@@ -488,7 +488,7 @@ struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
 }
 
 impl<K: Ord, V> BTreeMap<K, V> {
-    /// Makes a new empty BTreeMap with a reasonable choice for B.
+    /// Makes a new empty BTreeMap.
     ///
     /// Does not allocate anything on its own.
     ///