Update TestCase Source Code Link to V2 SDK (#1182)

Author: ChihweiLHBird

website/docs/plugin/sdkv2/testing/acceptance-tests/testcase.mdx

@@ -95,7 +95,7 @@ currently running.
 
 `TestCase` offers several fields for developers to add to customize and validate
 each test, defined below. The source for `TestCase` can be viewed [here on
-godoc.org](https://pkg.go.dev/github.com/hashicorp/terraform-plugin-sdk/helper/resource#TestCase)
+godoc.org](https://pkg.go.dev/github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource#TestCase)
 
 ### IsUnitTest