fix: avoid blocking modify monitor by redundant detect call

[wilmerdooley]

What's changed?

Removed the synchronous detectMonitor invocation from the modifyMonitor flow in MonitorServiceImpl. Previously, updating a monitor's settings (such as the collect interval) would trigger an immediate detection pass while still holding the monitor lock, which could block the request for a long time and eventually cause the API to time out even though the save itself succeeded.

The detection is no longer required as part of the update path; the collector will pick up the new configuration on its next scheduled run. This makes the modify monitor endpoint return promptly and prevents the misleading timeout-on-successful-save behavior reported by users.

Resolves #3812

Checklist

• I have read the Contributing Guide
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

Add or update API

• I have added the necessary e2e tests and all cases have passed.