helm: accept context and validate_certs (#74)

I've got the following environment variable set:
- `K8S_AUTH_VERIFY_SSL=False`

Helm's `validate_certs` parameter fallback on this environment variable.
Which means, on my system, the `validate_certs` will already be set.

So we cannot make this parameter exclusive wih another one.

plugins/modules/helm.py

@@ -519,9 +519,7 @@ def main():
         ],
         mutually_exclusive=[
             ("context", "ca_cert"),
-            ("context", "validate_certs"),
             ("kubeconfig", "ca_cert"),
-            ("kubeconfig", "validate_certs")
         ],
         supports_check_mode=True,
     )