NavigationMapRoute style documentation is outdated (style name changed)

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**Mapbox Navigation SDK version:**
Before:
```
implementation 'com.mapbox.navigation:ui-v1:1.0.0-SNAPSHOT'
implementation 'com.mapbox.navigation:core:1.0.0-rc.4'

```

After:

```
implementation 'com.mapbox.navigation:ui:1.0.0-rc.6'
implementation 'com.mapbox.navigation:core:1.0.0-rc.6'

<style name="mapbox_route" parent="MapboxStyleNavigationMapRoute">

```

### Steps to trigger behavior

1. Update to rc.6
2. See error that `NavigationMapRoute` does not exist anymore
3. Open `NavigationMapRoute.java`, read its docs, it says

>Inside your applications {@code style.xml} file, you extend {@code <style name="NavigationMapRoute">} [...]

### Expected behavior
Documentation is updated, should say "MapboxStyleNavigationMapRoute". I would also suggest to add something like ` <style name="mapbox_route" parent="MapboxStyleNavigationMapRoute">` as that makes it even more clear on how the extending works.

### Actual behavior
Documentation is not updated

Open NavigationMapRoute.java and find the style.xml documentation describing the NavigationMapRoute parent. Compare it with the rc.6 usage shown in the issue, including the mapbox_route style example. Done means the documentation names MapboxStyleNavigationMapRoute and clearly shows how to extend it.

Written by the indexing model from the issue text.