VoIP virtual rooms, mkII

or: remove the virtual room mapping config option

as per https://github.com/matrix-org/matrix-react-sdk/pull/5639

docs/config.md

@@ -110,18 +110,6 @@ For a good example, see https://develop.element.io/config.json.
    1. `logo`: An HTTP URL to the avatar for the desktop build. Should be 24x24, ideally
       an SVG.
    1. `url`: An HTTP URL for where to send the user to download the desktop build.
-1. `voip_mxid_translate_pattern`: Used to route VoIP calls to different Matrix IDs.
-   Any VoIP calls placed will instead be placed to the translated Matrix ID from the
-   pattern string but still appear to be with the original Matrix ID. Correspondingly,
-   incoming VoIP calls will be made to appear as if they came from a different Matrix ID.
-   The value is a template string with substitution `$(mxid)` which is the complete
-   URL-encoded native Matrix ID, using '=' instead of '%'. For example, a value of
-   `@_myappservice_$(mxid):example.org` would cause any VoIP call to `@bob:foo.example`
-   to be redirected to `@_myappservice_=40bob=3Afoo.example:example.org` and calls
-   from the latter to appear as if they were from the former.
-   This option is experimental and may be removed at any time without notice. It's
-   also strongly advised not to set this option unless you're absolutly certain you
-   know what you're doing.
 1. `mobileGuideToast`: Whether to show a toast a startup which nudges users on
    iOS and Android towards the native mobile apps. The toast redirects to the
    mobile guide if they accept. Defaults to false.