docs: fix broken links to dts-test files (#3034)

Author: haoqunjiang

src/guide/typescript/options-api.md

@@ -230,7 +230,7 @@ declare module 'vue' {
 
 See also:
 
-- [TypeScript unit tests for component type extensions](https://github.com/vuejs/core/blob/main/packages/dts-test/componentTypeExtensions.test-d.tsx)
+- [TypeScript unit tests for component type extensions](https://github.com/vuejs/core/blob/main/packages-private/dts-test/componentTypeExtensions.test-d.tsx)
 
 ### Type Augmentation Placement {#type-augmentation-placement}
 
@@ -290,4 +290,4 @@ The placement of this augmentation is subject to the [same restrictions](#type-a
 
 See also:
 
-- [TypeScript unit tests for component type extensions](https://github.com/vuejs/core/blob/main/packages/dts-test/componentTypeExtensions.test-d.tsx)
+- [TypeScript unit tests for component type extensions](https://github.com/vuejs/core/blob/main/packages-private/dts-test/componentTypeExtensions.test-d.tsx)

src/guide/typescript/overview.md

@@ -112,7 +112,7 @@ export default defineComponent({
 See also:
 
 - [Note on webpack Treeshaking](/api/general#note-on-webpack-treeshaking)
-- [type tests for `defineComponent`](https://github.com/vuejs/core/blob/main/packages/dts-test/defineComponent.test-d.tsx)
+- [type tests for `defineComponent`](https://github.com/vuejs/core/blob/main/packages-private/dts-test/defineComponent.test-d.tsx)
 
 :::tip
 `defineComponent()` also enables type inference for components defined in plain JavaScript.