Fix Jest test: Mock CallStore.getCall rather than individual hooks like useParticipants

[langleyd]

Relates to #30373

particularly the error here.

 ● RoomHeader › group call enabled › close lobby button is shown if there is an ongoing call but we are viewing the lobby

    TypeError: Cannot read properties of undefined (reading 'length')

      46 |         call ?? undefined,
      47 |         CallEvent.Participants,
    > 48 |         useCallback((state) => state ?? call?.participants ?? [], [call]),
         |                    ^
      49 |     );
      50 | };
      51 |

      at areHookInputsEqual (node_modules/react-dom/cjs/react-dom-client.development.js:5478:36)
      at updateCallback (node_modules/react-dom/cjs/react-dom-client.development.js:6595:28)
      at Object.useCallback (node_modules/react-dom/cjs/react-dom-client.development.js:23149:16)
      at Object.<anonymous>.process.env.NODE_ENV.exports.useCallback (node_modules/react/cjs/react.development.js:1161:34)
      at useParticipants (src/hooks/useCall.ts:48:20)
      at useParticipants (src/hooks/useCall.ts:53:26)
      at useRoomCall (src/hooks/room/useRoomCall.tsx:125:53)
      at RoomHeader (src/components/views/rooms/RoomHeader/RoomHeader.tsx:87:20)
      at Object.react_stack_bottom_frame (node_modules/react-dom/cjs/react-dom-client.development.js:23863:20)
      at renderWithHooks (node_modules/react-dom/cjs/react-dom-client.development.js:5529:22)
      at updateFunctionComponent (node_modules/react-dom/cjs/react-dom-client.development.js:8897:19)
      at beginWork (node_modules/react-dom/cjs/react-dom-client.development.js:10522:18)
      at runWithFiberInDEV (node_modules/react-dom/cjs/react-dom-client.development.js:1522:13)
      at performUnitOfWork (node_modules/react-dom/cjs/react-dom-client.development.js:15140:22)
      at workLoopSync (node_modules/react-dom/cjs/react-dom-client.development.js:14956:41)
      at renderRootSync (node_modules/react-dom/cjs/react-dom-client.development.js:14936:11)
      at performWorkOnRoot (node_modules/react-dom/cjs/react-dom-client.development.js:14462:44)
      at performSyncWorkOnRoot (node_modules/react-dom/cjs/react-dom-client.development.js:16231:7)
      at flushSyncWorkAcrossRoots_impl (node_modules/react-dom/cjs/react-dom-client.development.js:16079:21)
      at flushSyncWork$1 (node_modules/react-dom/cjs/react-dom-client.development.js:14721:12)
      at Object.f (node_modules/react-dom/cjs/react-dom-client.development.js:24396:26)
      at Object.<anonymous>.process.env.NODE_ENV.exports.flushSync (node_modules/react-dom/cjs/react-dom.development.js:140:23)
      at node_modules/@floating-ui/react-dom/dist/floating-ui.react-dom.umd.js:182:31

A change to floating-ui dependency seems to be calling flushSync which triggers a render of the component and doesn't play nice with this mocking specific hooks and not others.
It probably makes more sense to mock the store data so the hooks are consistent.