Tweak video rooms copy (#8582)

* "Video room" → "New video room"

* "Connect now" → "Join"

* "N people connected" → "N people joined"

* "Connected" → "Joined"

* Fix tests

src/components/structures/SpaceRoomView.tsx

@@ -136,7 +136,7 @@ const SpaceLandingAddButton = ({ space }) => {
                         }}
                     />
                     { videoRoomsEnabled && <IconizedContextMenuOption
-                        label={_t("Video room")}
+                        label={_t("New video room")}
                         iconClassName="mx_RoomList_iconNewVideoRoom"
                         onClick={async (e) => {
                             e.preventDefault();