Docs(lib/extract_if): Unify example description

Signed-off-by: Paul Mabileau <paul.mabileau@harfanglab.fr>

library/alloc/src/collections/linked_list.rs

@@ -1137,7 +1137,7 @@ pub fn retain_mut<F>(&mut self, mut f: F)
     ///
     /// # Examples
     ///
-    /// Splitting a list into evens and odds, reusing the original list:
+    /// Splitting a list into even and odd values, reusing the original list:
     ///
     /// ```
     /// use std::collections::LinkedList;

library/alloc/src/vec/mod.rs

@@ -3701,7 +3701,7 @@ pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoI
     ///
     /// # Examples
     ///
-    /// Splitting an array into evens and odds, reusing the original allocation:
+    /// Splitting a vector into even and odd values, reusing the original vector:
     ///
     /// ```
     /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];