docs: simplify titles of simple offboard api articles

docs/en/SUMMARY.md

@@ -34,7 +34,7 @@
     * [Marker detection](aruco_marker.md)
     * [Map-based navigation](aruco_map.md)
   * [Optical Flow](optical_flow.md)
-  * [Simple OFFBOARD](simple_offboard.md)
+  * [Autonomous flight (OFFBOARD)](simple_offboard.md)
   * [Coordinate systems (frames)](frames.md)
   * [Code snippets](snippets.md)
   * [Interfacing with a laser rangefinder](laser.md)

docs/en/simple_offboard.md

@@ -1,4 +1,4 @@
-Simple OFFBOARD
+Autonomous flight (OFFBOARD)
 ===
 
 > **Note** In the image version **0.20** `clever` package was renamed to `clover`. See [previous version of the article](https://github.com/CopterExpress/clover/blob/v0.19/docs/en/simple_offboard.md) for older images.

docs/ru/SUMMARY.md

@@ -35,7 +35,7 @@
     * [Распознавание маркеров](aruco_marker.md)
     * [Навигация по карте маркеров](aruco_map.md)
   * [Навигация по Optical Flow](optical_flow.md)
-  * [Автономный полет в OFFBOARD](simple_offboard.md)
+  * [Автономный полет (OFFBOARD)](simple_offboard.md)
   * [Системы координат](frames.md)
   * [Примеры кода](snippets.md)
   * [Лазерный дальномер](laser.md)