Fix example of programmatic Timer creation

[glebfox]

Environment

• Documentation version: 7.0+
• Part of the documentation: Manual
• Existing page: https://doc.cuba-platform.com/manual-7.1/gui_Timer.html

Description of the bug or enhancement

The following example of programmatic Timer creation is no longer valid:

Timer helloTimer = uiComponents.create(Timer.NAME);

Starting from v7.0 the Facet bean must be used:

@Inject
private Facets facets;
...
Timer timer = facets.create(Timer.class);