fix(cli): use bracket notation for index signature access in tests

packages/cli/src/ui/commands/experimentCommand.test.ts

@@ -122,10 +122,9 @@ describe('experimentCommand', () => {
     );
 
     it('should unset an experiment', async () => {
-       
-      (
-        mockContext.services.settings.merged as Record<string, unknown>
-      ).experimental = {
+      (mockContext.services.settings.merged as Record<string, unknown>)[
+        'experimental'
+      ] = {
         'enable-preview': true,
       };
       await unsetCommand?.action!(mockContext, 'enable-preview');