Use a better attribute name

Author: javiereguiluz

src/Icons/doc/index.rst

@@ -544,10 +544,10 @@ Full Configuration
         # The local directory where icons are stored
         icon_dir: '%kernel.project_dir%/assets/icons'
 
-        # Default attributes to add to all icons.
+        # Default attributes to add to all icons
         default_icon_attributes:
             fill: currentColor
-            'aria-hidden': true
+            'font-size': '1.25em'
 
         # Icon aliases (alias => icon name)
         aliases: