Examples in documentation are using deprecated code

### Module version
v1.12.x (latest version)

### Expected Behavior
Code examples do not contain deprecated SDKv2 code.

### Actual Behavior

During research how to obtain the client inside the _checkDestroy()_ function for the _terraform-plugin-testing_ I came across that the documentation still contains old SDKv2 (deprecated) code.

CheckDestroy() documentation with example:
[checkDestroy](https://developer.hashicorp.com/terraform/plugin/testing/acceptance-tests/testcase#checkdestroy)

This example is the same as for the SDKv2 and is using _Providers:_ inside the test which gets an _*schema.Provider_ as input. This is not possible by using the _github.com/hashicorp/terraform-plugin-testing_.

Can you please update the examples or describe how to obtain the client inside the _checkDestroy()_ function which is already used by the test to create/update/destroy resources? Currently we are creating a new separate client in the _checkDestroy()_ but want to use the same as the test is already using.