feat(gz): update submodule, and add ridge docs (#27600)

* feat(gz): update submodule, and add ridge docs

docs/en/releases/1.18.md

@@ -69,6 +69,7 @@ Please continue reading for [upgrade instructions](#upgrade-guide).
 
 ### Simulation
 
+- Gazebo: Add [ridge world](../sim_gazebo_gz/worlds.md#ridge) for testing terrain following with 1D lidar. ([PX4-Autopilot#27600](https://github.com/PX4/PX4-Autopilot/pull/27600))
 - SIH: Add option to set wind velocity ([PX4-Autopilot#26467](https://github.com/PX4-Autopilot/pull/26467))
 
 <!-- MOVED THIS TO v1.17

docs/en/sim_gazebo_gz/index.md

@@ -173,6 +173,7 @@ The [supported worlds](../sim_gazebo_gz/worlds.md) are listed below.
 | `baylands`        | `make px4_sitl *_baylands`        | Baylands world surrounded by water                          |
 | `lawn`            | `make px4_sitl *_lawn`            | Lawn world for testing rovers                               |
 | `rover`           | `make px4_sitl *_rover`           | Rover world (optimised/preferred)                           |
+| `ridge`           | `make px4_sitl *_ridge`           | World with a sloped ridge for testing terrain following     |
 | `walls`           | `make px4_sitl *_walls`           | Wall world for testing collision prevention                 |
 | `windy`           | `make px4_sitl *_windy`           | Empty world with wind enabled                               |
 | `moving_platform` | `make px4_sitl *_moving_platform` | World with moving takeoff / landing platform                |

docs/en/sim_gazebo_gz/worlds.md

@@ -43,6 +43,28 @@ It is not recommended as the low frame rate causes segmentation faults on some f
 
 ![screenshot of lawn world](../../assets/simulation/gazebo/worlds/lawn.png)
 
+## Ridge
+
+<Badge type="tip" text="PX4 v1.18" />
+
+World with a simple sloped ridge for testing terrain following.
+It pairs naturally with the [x500_lidar_down](../sim_gazebo_gz/vehicles.md#x500-quadrotor-with-1d-lidar-down-facing) airframe:
+
+```sh
+PX4_GZ_WORLD=ridge make px4_sitl gz_x500_lidar_down
+```
+
+Layout:
+
+- 500x500 m flat ground at world `z = 0`.
+- A 40 m wide, 10 m tall, 40 m long triangular-prism ridge ~20 m east of the spawn (apex at world `(40, 0, 10)`).
+  The ridge is continuously sloped (~27°) so the rangefinder reading varies smoothly as the vehicle crosses it, avoiding the spurious EKF terrain-estimate resets that a vertical wall would trigger.
+- Spherical coordinates are anchored at `(47.397971, 8.546164, 0)` so home AMSL is 0 by default; raise the elevation to test against non-zero AMSL anchors.
+
+[PX4-gazebo-models/main/worlds/ridge.sdf](https://github.com/PX4/PX4-gazebo-models/blob/main/worlds/ridge.sdf)
+
+![screenshot of ridge world](../../assets/simulation/gazebo/worlds/ridge.png)
+
 ## Rover
 
 Rover world is optimised for rovers (and will be further optimised for rovers) and is the default world for [Ackermann Rover (4012)](../frames_rover/index.md#ackermann) (`make px4_sitl gz_rover_ackermann`) and [Differential Rover ((r1-rover (4009))](../frames_rover/index.md#differential) (`make px4_sitl gz_r1_rover`).
@@ -97,7 +119,7 @@ The moving platform plugin can also be used within other worlds.
 For more information, see the plugin [README](https://github.com/PX4/PX4-Autopilot/blob/main/src/modules/simulation/gz_plugins/moving_platform_controller/README.md).
 :::
 
-## Model Specific Worlds {#model_specific_worlds}
+## Model-specific Worlds {#model_specific_worlds}
 
 Some [vehicle models](../sim_gazebo_gz/vehicles.md) rely on the physics / plugins of a specific world.
 The PX4 toolchain will automatically spawn a world that has the same name as the vehicle model if one exists (instead of the [default world](#default)):