[Security Solution] Adjust Cypress buildkite job config

[patrykkopycinski]

Summary

Due to #158236 there is no need to run Security Solution Cypress tests on 15 buildkite agents anymore

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 1eb1d35

Failed CI Steps

• Security Solution Tests #1

Test Failures

• [job] [logs] Security Solution Tests #1 / Entity Analytics Dashboard With anomalies data renders table with pagination

Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
securitySolution	414	418	+4
total			+6

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
securitySolution	498	502	+4
total			+6

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@elasticmachine merge upstream