More documentation consistency fixes

Author: balt-dev

library/alloc/src/collections/linked_list.rs

@@ -825,7 +825,7 @@ impl<T, A: Allocator> LinkedList<T, A> {
         unsafe { self.tail.as_mut().map(|node| &mut node.as_mut().element) }
     }
 
-    /// Adds an element first in the list.
+    /// Adds an element to the front of a list.
     ///
     /// This operation should compute in *O*(1) time.
     ///
@@ -847,7 +847,7 @@ impl<T, A: Allocator> LinkedList<T, A> {
         let _ = self.push_front_mut(elt);
     }
 
-    /// Adds an element first in the list, returning a reference to it.
+    /// Adds an element to the front of a list, returning a reference to it.
     ///
     /// This operation should compute in *O*(1) time.
     ///