Switch to the new session API for screen-sharing (#11266)

See https://github.com/electron/electron/pull/30702 - this has the benefit of the js-sdk and LiveKit not having to add custom logic for Electron

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/stores/widgets/ElementWidgetActions.ts

@@ -27,19 +27,6 @@ export enum ElementWidgetActions {
     UnmuteVideo = "io.element.unmute_video",
     StartLiveStream = "im.vector.start_live_stream",
 
-    // Element Call -> host requesting to start a screenshare
-    // (ie. expects a ScreenshareStart once the user has picked a source)
-    // replies with { pending } where pending is true if the host has asked
-    // the user to choose a window and false if not (ie. if the host isn't
-    // running within Electron)
-    ScreenshareRequest = "io.element.screenshare_request",
-    // host -> Element Call telling EC to start screen sharing with
-    // the given source
-    ScreenshareStart = "io.element.screenshare_start",
-    // host -> Element Call telling EC to stop screen sharing, or that
-    // the user cancelled when selecting a source after a ScreenshareRequest
-    ScreenshareStop = "io.element.screenshare_stop",
-
     // Actions for switching layouts
     TileLayout = "io.element.tile_layout",
     SpotlightLayout = "io.element.spotlight_layout",