Updating contributing doc to add the correct helm and bats versions (h…

…ashicorp#1314)

CONTRIBUTING.md

@@ -573,15 +573,15 @@ very quickly. These should be used for fast feedback during development.
 The acceptance tests require a Kubernetes cluster with a configured `kubectl`.
 
 ### Prerequisites
-* [Bats](https://github.com/bats-core/bats-core)
+* [Bats](https://github.com/bats-core/bats-core) (Currently, must use v1.6.0+.)
   ```bash
   brew install bats-core
   ```
 * [yq](https://pypi.org/project/yq/)
   ```bash
   brew install python-yq
   ```
-* [Helm 3](https://helm.sh) (Currently, must use v3.6.3. Also, Helm 2 is not supported) 
+* [Helm 3](https://helm.sh) (Currently, must use v3.8.0+.) 
   ```bash
   brew install kubernetes-helm
   ```