Link in https://github.com/googleapis/google-cloud-java/blob/main/README.md#testing broken

https://github.com/googleapis/google-cloud-java/blob/main/README.md#testing has the following link:

"See [TESTING] to read more about using our testing helpers."

The link is broken:
https://github.com/googleapis/google-cloud-java/blob/main/TESTING.md

404 - page not found
The main branch of google-cloud-java does not contain the path TESTING.md

