Disable proactive rerouting, route refreshing after map matching

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The “Custom Server” example relies on the Map Matching API to derive a route from a series of waypoints. This example is intended for a “Bring Your Own Route” use case where the waypoints are control points from a route produced by another routing engine. In that case, proactive rerouting would automatically undo any customization implemented through the BYOR workflow. The route refreshing functionality added in mapbox/mapbox-navigation-ios#2284 would also fail because the route doesn’t come from the Directions API but is instead synthesized on the client-side.

The navigation SDK has no way to distinguish a Route obtained through `Directions.calculateRoutes(matching:completionHandler:)` from one obtained through `calculate(_:completionHandler:)`. So it falls to the developer to disable proactive rerouting and route refreshing manually:

```swift
let router = navigationViewController.navigationService.router
router.reroutesProactively = false
router.refreshesRoute = false
```

We should add these lines to the “Custom Server” example:

https://github.com/mapbox/navigation-ios-examples/blob/e85b6f530e7b6a0e9fe8f18f5d22472323e43eb7/Navigation-Examples/Examples/Custom-Server.swift#L30-L33

/cc @mapbox/navigation-ios

Open Navigation-Examples/Examples/Custom-Server.swift around lines 30–33 and review how the navigation service router is configured. Disable proactive rerouting and route refreshing for this example, then build or run the Custom Server example to confirm the BYOR route remains unchanged.

Written by the indexing model from the issue text.