Verify (and update) the commit SHA of googletest within the cgmanifest.json files in the repo

Is this the actual commit we are using?

_Originally posted by @LarryOsterman in https://github.com/Azure/azure-sdk-for-cpp/pull/6176#discussion_r1829825941_

https://github.com/Azure/azure-sdk-for-cpp/blob/3687136d04cc8e425cb368ce879a1686834b17c9/sdk/template/azure-template/cgmanifest.json#L8-L9

This is the SHA that's specified in the template, keyvault, eventhubs, and attestation packages. If we need to update it, we'd want to do so everywhere in the repo.