Fix incorrect reference to BrowserStateKeyedServiceFactory

The factories classes in //chrome/browser inherits from either
ProfileKeyedServiceFactor or BrowserContextKeyedServiceFactory
but not BrowserStateKeyedServiceFactory.

Fix the "// BrowserContextKeyedServiceFactory implementation"
comments to refer to the correct class.

Bug: none
Change-Id: I4cec185b5cb4f7c1b4ef2603aa2f1931c7d59e14
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6911181
Reviewed-by: David Roger <droger@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1510096}