[AssetMapper] Minor

Page: https://symfony.com/doc/6.4/frontend/asset_mapper.html#handling-css

This is indeed better than #19453 was; and much better than before.

1. "valid" in which sense? Valid importmap syntax?

Author: ThomasLandauer

frontend/asset_mapper.rst

@@ -421,8 +421,8 @@ the page as ``link`` tags in the order they were imported.
 
     Importing a CSS file is *not* something that is natively supported by
     JavaScript modules. AssetMapper makes this work by adding a special importmap
-    entry for each CSS file. These special entries are valid valid, but do nothing.
-    AssetMapper adds a ``<link>`` tag for each CSS file, but when the JavaScript
+    entry for each CSS file. These special entries are valid, but do nothing.
+    AssetMapper adds a ``<link>`` tag for each CSS file, but when JavaScript
     executes the ``import`` statement, nothing additional happens.
 
 .. _asset-mapper-3rd-party-css: