Update index.bs

Co-authored-by: Julian Descottes <[email protected]>

Author: sadym-chromium

index.bs

@@ -6363,7 +6363,7 @@ The <dfn export>WebDriver BiDi emulated User-Agent</dfn> steps given
 
 <div algorithm="remote end steps for emulation.setUserAgentOverride">
 
-The [=remote end steps=] with |command parameters| are:
+The [=remote end steps=] given |session|  and |command parameters| are:
 
 1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
    and |command parameters| [=map/contains=] "<code>context</code>",