Deprecate OpenSearch 1 support

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Context

OpenSearch 1 is deprecated and no longer maintained by AWS. Advanced Search currently allows for OpenSearch 1 to 3 but should not allow OpenSearch 1.

https://opensearch.org/releases/#maintenance-policy

We need to determine how to get customers running OpenSearch 1 over to 2/3 without interruption.

JTBD

Make OpenSearch 1 unsupported for Advanced Search.

• Determine how to make this a non-breaking change for customers running OpenSearch 1
• Update search check to make OpenSearch 1 unsupported: https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/system_check/app/search_check.rb
• Update Elasticsearch integration docs to indicate support: https://docs.gitlab.com/integration/advanced_search/elasticsearch/#opensearch
• Update CI Pipelines to remove os1-services for gitlab project
• Update CI Pipelines to remove OS 1.X for gitlab-elasticsearch-indexer project