Remove space-specific right panel store handling

This is no longer needed as the right panel always corresponds to the currently viewed room/space only.

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

test/unit-tests/components/views/rooms/PinnedMessageBanner-test.tsx

@@ -224,7 +224,7 @@ describe("<PinnedMessageBanner />", () => {
             // The Right panel is opened on another card
             jest.spyOn(RightPanelStore.instance, "isOpenForRoom").mockReturnValue(true);
             jest.spyOn(RightPanelStore.instance, "currentCard", "get").mockReturnValue({
-                phase: RightPanelPhases.RoomMemberList,
+                phase: RightPanelPhases.MemberList,
             });
 
             renderBanner();