do not set development mode when running vitest

[Fallsleep]

For convenience, I want to reuse the .env.development.local instead creating a specific .env.test .

For this, I change the test script to vitest --mode development and add import.meta.env.MODE = 'test' in the vitest.setup.ts to reset mode.

Then, most of the test run well, but when I test pinia action calling, I got TypeError: [Function] is not a spy or a call to a spy! like reproduction.

As I returned a Promise in the action, I think there's someting wrong with vi.fn or pinia/testing for Promise at first.

In order to find the reason, I add an example on stackblitz for reproduction, but the test running no error!

After a lot of try, include upgrade vite/vitest/pinia/happy-dom and get many other error, I found out the test script is deffirent in my project and the reproduction.

I use vitest --mode development in my project, while vitest in the reproduction.

When I add --mode development in the reproduction, it also throw TypeError: [Function] is not a spy or a call to a spy!

So, don't set development mode when running vitest, it may course unkown error.

I also add a discussion in vitest-dev/vitest#2955