remove vitest imports from test files

Author: ryoppippi

src/tool.test-d.ts

@@ -1,5 +1,4 @@
 import type { ChatCompletionFunctionTool } from 'openai/resources/chat/completions';
-import { assertType, test } from 'vitest';
 import { BaseTool, Tools } from './tool';
 import type { AISDKToolResult } from './types';
 

src/tool.test.ts

@@ -1,4 +1,3 @@
-import { assert } from 'vitest';
 import { jsonSchema } from 'ai';
 import type { JSONSchema7 } from 'json-schema';
 import { BaseTool, type MetaToolSearchResult, StackOneTool, Tools } from './tool';