[Security Solution] Clean connectors before custom query rule test

[lgestc]

Summary

Connector list is not cleaned up currently which prevents running custom_query_rule.cy.ts more than once after bootstrap (manually from the cypress UI). This PR ensures that the connector list is cleaned up properly.

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 8320dea

Metrics [docs]

Unknown metric groups

ESLint disabled in files

id	before	after	diff
osquery	1	2	+1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
fleet	61	67	+6
osquery	109	115	+6
securitySolution	439	445	+6
total			+20

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	70	76	+6
osquery	110	117	+7
securitySolution	515	521	+6
total			+21

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@elasticmachine merge upstream

[maximpn]

Rules Area LGTM

@lgmys thanks for the improvement!

I'm curious though if this issue happens in the other test files. If that's the case it would be nice to fix for all rule types.