Make wording in documentation for LinkedList::push_front_mut, etc. consistent with VecDeque and Vec

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 to the front of a list.
+    /// Adds an element to the front of the 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 to the front of a list, returning a reference to it.
+    /// Adds an element to the front of the list, returning a reference to it.
     ///
     /// This operation should compute in *O*(1) time.
     ///
@@ -899,7 +899,7 @@ impl<T, A: Allocator> LinkedList<T, A> {
         self.pop_front_node().map(Node::into_element)
     }
 
-    /// Adds an element to the back of a list.
+    /// Adds an element to the back of the list.
     ///
     /// This operation should compute in *O*(1) time.
     ///
@@ -919,7 +919,7 @@ impl<T, A: Allocator> LinkedList<T, A> {
         let _ = self.push_back_mut(elt);
     }
 
-    /// Adds an element to the back of a list, returning a reference to it.
+    /// Adds an element to the back of the list, returning a reference to it.
     ///
     /// This operation should compute in *O*(1) time.
     ///