updating test for strict mode and non strict mode consistency

the previous expect was relying on the fact that ButtonGroup first measurement happened before we mock the widths and positions of the buttons + buttongroups. That doesnt work well in strict mode and didnt feel reflective of browser behavior so I removed that expect

packages/@react-spectrum/buttongroup/test/ButtonGroup.test.js

@@ -125,7 +125,6 @@ describe('ButtonGroup', function () {
   describe('resizing', () => {
     it('goes vertical if there is not enough room after buttongroup gets a new size', () => {
       let setUp = ({buttonGroup, button1, button2, button3}) => {
-        // can't do anything about first render, so this starts with the resize
         jest.spyOn(buttonGroup, 'offsetWidth', 'get').mockImplementationOnce(() => 88).mockImplementation(() => 90);
         jest.spyOn(button1, 'offsetLeft', 'get').mockImplementation(() => 0);
         jest.spyOn(button1, 'offsetWidth', 'get').mockImplementation(() => 30);
@@ -138,14 +137,6 @@ describe('ButtonGroup', function () {
       let {getByTestId} = render(<ButtonGroupWithRefs setUp={setUp} />);
       let buttonGroup = getByTestId(buttonGroupId);
 
-      if (process.env.STRICT_MODE) {
-        // If strict mode, render cycle happens twice which means a 2nd useLayoutEffect is triggered -> mock widths are now already set since
-        // ButtonGroupWithRefs's useEffect has already run
-        expect(buttonGroup).toHaveAttribute('class', expect.stringContaining('spectrum-ButtonGroup--vertical'));
-      } else {
-        expect(buttonGroup).not.toHaveAttribute('class', expect.stringContaining('spectrum-ButtonGroup--vertical'));
-      }
-
       // ResizeObserver not actually implemented in jsdom, so rely on the fallback to window resize listener
       act(() => {window.dispatchEvent(new Event('resize'));});
       expect(buttonGroup).toHaveAttribute('class', expect.stringContaining('spectrum-ButtonGroup--vertical'));