Prepare v6 changelog (again++)

Author: mpalourdio

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## v6.0.0
 - The `subscription` in `NgHttpLoaderComponent` has completely been removed in favor of an `observable`. As there's no need to unsubscribe anymore, `ngOnDestroy` has been removed.
 - The `observable` initialization has been moved to `ngOnInit`.
-- The test suite could fail (and succeed) in some unexpected ways. This was caused by timing/subscriptions issues which are now (hopefully) fixed.
+- The test suite could fail (and succeed) in some unexpected ways. This was caused by some race conditions introduced in v5.0.0. Those are now (hopefully) fixed.
 - Angular 8.x is now the default supported version.
 
 ## v5.1.0