[Bug] elasticstack_kibana_alerting_rule without elasticsearch configuration

[fabienduval]

Describe the bug
elasticstack_kibana_alerting_rule without an elasticsearch configuration, usage became impossible.

To Reproduce
Steps to reproduce the behavior:

1. Configure the provider with only a kibana configuration, no elasticsearch
   provider "elasticstack" { kibana {} }
2. Use a version between 0.11.7 and 0.11.9 of the provider
3. Declare a kibana alerting rule - elasticstack_kibana_alerting_rule
4. terraform init, terraform plan => there are no issue here
5. terraform apply fails, with the following error
   Error: elasticsearch client not found
6. Downgrade the provider to version 0.11.6
7. terraform init, terraform apply
8. The alert is succesfully configured.

Expected behavior
It should work the same way as with the version 0.11.6.

Versions (please complete the following information):

• OS: Linux
• Terraform Version 1.9.6
• Provider version 0.11.7
• Elasticsearch Version 8.15.0

[tobio]

Thanks for reporting this @fabienduval, it'll be fixed up in the next release.