message: Add even more stability to view source test case
  Follow-on from after seeing more failures from the test case.
diff: @@ -238,7 +238,7 @@ describe("Timeline", () => {
  cy.contains(".mx_RoomView_body .mx_EventTile[data-scroll-tokens]", "MessageEdit").should("exist");
  // Click top left of the event toggle, which should not be covered by MessageActionBar's safe area
  - cy.get(".mx_EventTile .mx_ViewSourceEvent").realHover().within(() => {
  + cy.get(".mx_EventTile .mx_ViewSourceEvent").should("exist").realHover().within(() => {
  cy.get(".mx_ViewSourceEvent_toggle").click('topLeft', { force: false });
  });
  