Fix failing ipywidget tests (microsoft#11132)

For #11099

Author: DonJayamanne

src/test/datascience/ipywidgets/localWidgetScriptSourceProvider.unit.test.ts

@@ -112,9 +112,9 @@ suite('Data Science - ipywidget - Local Widget Script Source', () => {
  metadata: { interpreter: { sysPrefix, path: 'pythonPath' } }
  } as any);
  when(fs.search(anything(), anything())).thenResolve([
- 'widget1/index.js',
- 'widget2/index.js',
- 'widget3/index.js'
+ path.join('widget1', 'index.js'),
+ path.join('widget2', 'index.js'),
+ path.join('widget3', 'index.js')
  ]);
 
  const value = await scriptSourceProvider.getWidgetScriptSource('widget2', '1');
@@ -138,9 +138,9 @@ suite('Data Science - ipywidget - Local Widget Script Source', () => {
  metadata: { interpreter: { sysPrefix, path: 'pythonPath' } }
  } as any);
  when(fs.search(anything(), anything())).thenResolve([
- 'widget1/index.js',
- 'widget2/index.js',
- 'widget3/index.js'
+ path.join('widget1', 'index.js'),
+ path.join('widget2', 'index.js'),
+ path.join('widget3', 'index.js')
  ]);
 
  const value = await scriptSourceProvider.getWidgetScriptSource('widget1', '1');
@@ -162,9 +162,9 @@ suite('Data Science - ipywidget - Local Widget Script Source', () => {
  metadata: { interpreter: { sysPrefix, path: 'pythonPath' } }
  } as any);
  when(fs.search(anything(), anything())).thenResolve([
- 'widget1/index.js',
- 'widget2/index.js',
- 'widget3/index.js'
+ path.join('widget1', 'index.js'),
+ path.join('widget2', 'index.js'),
+ path.join('widget3', 'index.js')
  ]);
 
  const value = await scriptSourceProvider.getWidgetScriptSource('widgetNotFound', '1');