[terraform-ibm-icd-elasticsearch] add fix to exclude group from point in time recovery

[ocofaigh]

The same fix as terraform-ibm-modules/terraform-ibm-icd-postgresql#525 is needed in Elasticsearch

[jor2]

https://github.com/terraform-ibm-modules/terraform-ibm-icd-elasticsearch/pull/330/files#diff-dc46acf24afd63ef8c556b77c126ccc6e578bc87e3aa09a931f33d9bf2532fbbR114

[jor2]

#330