[WebProfiler] add missing typehint to RouterController

It must be a RouteCollection because TraceableUrlMatcher expects it anyway.

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| License       | MIT