[Guided onboarding] Update codeowners for guided onboarding in the se…

…curity solution (#145555)

## Summary

Updates the codeowners file for the Security onboarding tour, that is
now owned by the team @elastic/security-threat-hunting-explore

.github/CODEOWNERS

@@ -661,8 +661,8 @@ x-pack/test/threat_intelligence_cypress @elastic/protections-experience
 /x-pack/test/api_integration/apis/cloud_security_posture/ @elastic/kibana-cloud-security-posture
 
 # Security Solution onboarding tour
-/x-pack/plugins/security_solution/public/common/components/guided_onboarding @elastic/platform-onboarding
-/x-pack/plugins/security_solution/cypress/e2e/guided_onboarding @elastic/platform-onboarding
+/x-pack/plugins/security_solution/public/common/components/guided_onboarding @elastic/security-threat-hunting-explore
+/x-pack/plugins/security_solution/cypress/e2e/guided_onboarding @elastic/security-threat-hunting-explore
 
 # Design (at the bottom for specificity of SASS files)
 **/*.scss  @elastic/kibana-design