[internal] PlzDedicatedWorker breaks worker networking

[dgozman]

See https://github.com/microsoft/playwright/pull/31705 for a failed roll.

Two tests are failing:

• [chromium-page] › page/interception.spec.ts:125:3 › should intercept network activity from worker 2
• [chromium-page] › page/workers.spec.ts:228:3 › should support extra http headers

Regressed in https://chromium-review.googlesource.com/c/chromium/src/+/5671624 by enabling PlzDedicatedWorker feature. Upstream issues:

• https://issues.chromium.org/u/1/issues/352584425 for interception;
• https://issues.chromium.org/u/1/issues/352528978 for extra headers.

Temporary resolution is to roll with PlzDedicatedWorker feature disabled, but we need upstream issues to be fixed and re-enable the feature.