Update integrations endpoint custom apdex targets

What does this MR do and why?

This MR sets low urgency Apdex thresholds for integrations controller actions that are used to test, and retry, integrations and webhooks.

When testing webhooks and integrations, requests might take longer than the default threshold of 1s due to the external server being tested against, and the experience for the user is not degraded.

See: https://gitlab.com/gitlab-org/gitlab/-/issues/343602.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #343602