Bump to 9.0.0-rc1 (#3177)

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:pipeline:猬嗭笍 Upload Pipeline: .buildkite/build_pr_pipeline.ymlbuildkite-agent pipeline upload .buildkite/build_pr_pipeline.yml
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.buildkite/scripts/cancel_running_pr.sh || true.buildkite/scripts/cancel_running_pr.sh || true
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setupcurl -s -L \ && -X POST \ && -H "Accept: application/vnd.github+json" \ && -H "Authorization: Bearer ${VAULT_GITHUB_TOKEN}" \ && -H "X-GitHub-Api-Version: 2022-11-28" \ && "https://api.github.com/repos/elastic/elasticsearch/statuses/6c7ed1ae22d4d18f1e99c8001c67ff1eff1051e5" \ && -d '{"state":"pending","target_url":"'https://buildkite.com/elastic/docs-build-pr/builds/291691'","description":"Build started","context":"buildkite/'docs-build-pr'"}'
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馃敤 Build docs PR.buildkite/scripts/build_pr.sh
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teardownstatus_state=failure && if [ $(buildkite-agent step get "outcome" --step "build-pr") == "passed" ]; then && status_state=success && fi && export status_state && curl -s -L \ && -X POST \ && -H "Accept: application/vnd.github+json" \ && -H "Authorization: Bearer ${VAULT_GITHUB_TOKEN}" \ && -H "X-GitHub-Api-Version: 2022-11-28" \ && "https://api.github.com/repos/elastic/elasticsearch/statuses/6c7ed1ae22d4d18f1e99c8001c67ff1eff1051e5" \ && -d '{"state":"'$status_state'","target_url":"'https://buildkite.com/elastic/docs-build-pr/builds/291691'","description":"Build finished","context":"buildkite/'docs-build-pr'"}'
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Total Job Run Time: 1m 11s