Add warning that simulated throttling doesn't seem to throttle User Timing measures

1. Run LH on Https://www.target.com using Simulated
2. Compare to running on Applied
#### What is the current behavior?

Note that most timings are <2s and faster than even FCP as reported at the top of the report.
When run on applied, the numbers are 4+x slower matching what you would expect from the report.

#### What is the expected behavior?
Timings on the page should line up such that custom timings are also throttled.

This is important for developers that build custom dashboards pulling timings from a LH run. Graphing out all timings from the LH report would lead to an incorrect representation of the order the timings fire (ex: A Custom Hero-timing could fire before FCP)

#### Environment Information
* Affected Channels: CLI, Extension, Dev Tools
* Lighthouse version: 5.4.0

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