DOC fix typo and improve whatsnew of scikit-learn#31665 (scikit-learn#31669)

Co-authored-by: Jérémie du Boisberranger <jeremie@probabl.ai>
Co-authored-by: Virgil Chan <virchan.math@gmail.com>

Author: 3 people

doc/whats_new/upcoming_changes/sklearn.linear_model/31665.enhancement.rst

@@ -1,3 +1,4 @@
 - class:`linear_model:ElasticNet` and class:`linear_model:Lasso` with
-  `precompute=False` uses less memory for dense `X` and is a bit faster.
+  `precompute=False` use less memory for dense `X` and are a bit faster.
+  Previously, they used twice the memory of `X` even for Fortran-contiguous `X`.
   By :user:`Christian Lorentzen <lorentzenchr>`