fix: mocking is lost with threads: false

closes #482

packages/vitest/src/runtime/entry.ts

@@ -1,6 +1,5 @@
 import { promises as fs } from 'fs'
 import type { BuiltinEnvironment, ResolvedConfig } from '../types'
-import { vi } from '../integrations/vi'
 import { setupGlobalEnv, withEnv } from './setup'
 import { startTests } from './run'
 
@@ -17,8 +16,6 @@ export async function run(files: string[], config: ResolvedConfig): Promise<void
 
     process.__vitest_worker__.filepath = file
 
-    vi.restoreAllMocks()
-
     await withEnv(env as BuiltinEnvironment, config.environmentOptions || {}, async() => {
       await startTests([file], config)
     })