Merge branch '6.4' into 7.0

* 6.4:
  [AssetMapper] Shortening "Optimizing Performance"

Author: javiereguiluz

frontend/asset_mapper.rst

@@ -611,7 +611,7 @@ To make your AssetMapper-powered site fly, there are a few things you need to
 do. If you want to take a shortcut, you can use a service like `Cloudflare`_,
 which will automatically do most of these things for you:
 
-- **Use HTTP/2**: Your web server **must** be running HTTP/2 (or HTTP/3) so the
+- **Use HTTP/2**: Your web server should be running HTTP/2 (or HTTP/3) so the
   browser can download assets in parallel. HTTP/2 is automatically enabled in Caddy
   and can be activated in Nginx and Apache. Or, proxy your site through a
   service like Cloudflare, which will automatically enable HTTP/2 for you.
@@ -625,13 +625,13 @@ which will automatically do most of these things for you:
   whitespace and comments from JavaScript and CSS files).
 
 - **Set long-lived Expires headers**: Your web server should set long-lived
-  Expires headers on your assets. Because the AssetMapper component includes a version
-  hash in the filename of each asset, you can safely set the Expires header
+  ``Expires`` HTTP headers on your assets. Because the AssetMapper component includes a version
+  hash in the filename of each asset, you can safely set the ``Expires`` header
   to a very long time in the future (e.g. 1 year). This isn't automatic in
   any web server, but can be easily enabled.
 
 Once you've done these things, you can use a tool like `Lighthouse`_ to
-validate the performance of your site!
+check the performance of your site.
 
 .. _performance-preloading: