Remove iron workflow and update readme (#434)

Co-authored-by: Alejandro Hernández Cordero <[email protected]>

.github/dependabot.yml

@@ -24,4 +24,4 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
-    target-branch: "iron"
+    target-branch: "jazzy"

README.md

@@ -12,10 +12,6 @@ This package provides a Gazebo-Sim system plugin which instantiates a `ros2_cont
 ROS version | Gazebo version | Branch | Binaries hosted at | APT key
 -- | -- | -- | -- | --
 Humble | Fortress | [humble](https://github.com/ros-controls/gz_ros2_control/tree/humble) | https://packages.ros.org | `ros-humble-ign-ros2-control`
-Iron | Edifice | [iron](https://github.com/ros-controls/gz_ros2_control/tree/iron) | only from source |
-Iron | Fortress | [iron](https://github.com/ros-controls/gz_ros2_control/tree/iron) | https://packages.ros.org | `ros-iron-gz-ros2-control`
-Iron | Garden | [iron](https://github.com/ros-controls/gz_ros2_control/tree/iron) | only from source |
-Iron | Harmonic | [iron](https://github.com/ros-controls/gz_ros2_control/tree/iron) | only from source |
 Jazzy | Harmonic | [jazzy](https://github.com/ros-controls/gz_ros2_control/tree/jazzy) | https://packages.ros.org | `ros-jazzy-gz-ros2-control`
 Rolling | Harmonic | [rolling](https://github.com/ros-controls/gz_ros2_control/tree/rolling) | https://packages.ros.org | `ros-rolling-gz-ros2-control`
 
@@ -25,7 +21,6 @@ ROS 2 Distro | Branch | Build status | Documentation
 :----------: | :----: | :----------: | :-----------:
 **Rolling** | [`rolling`](https://github.com/ros-controls/gz_ros2_control/tree/rolling) | [![gazebo_ros2_control CI - Rolling](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-rolling.yaml/badge.svg?branch=rolling)](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-rolling.yaml) | [Documentation](https://control.ros.org/rolling/index.html) <br /> [API Reference](https://control.ros.org/rolling/doc/api/index.html)
 **Jazzy** | [`jazzy`](https://github.com/ros-controls/gz_ros2_control/tree/jazzy) | [![gazebo_ros2_control CI - Jazzy](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-jazzy.yaml/badge.svg?branch=rolling)](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-jazzy.yaml) | [Documentation](https://control.ros.org/jazzy/index.html) <br /> [API Reference](https://control.ros.org/jazzy/doc/api/index.html)
-**Iron** | [`iron`](https://github.com/ros-controls/gz_ros2_control/tree/iron) | [![gazebo_ros2_control CI - Iron](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-iron.yaml/badge.svg?branch=iron)](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-iron.yaml) | [Documentation](https://control.ros.org/iron/index.html) <br /> [API Reference](https://control.ros.org/iron/doc/api/index.html)
 **Humble** | [`humble`](https://github.com/ros-controls/gz_ros2_control/tree/humble) | [![ign_ros2_control CI - Humble](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-humble.yaml/badge.svg?branch=humble)](https://github.com/ros-controls/gz_ros2_control/actions/workflows/ci-humble.yaml) | [Documentation](https://control.ros.org/humble/index.html) <br /> [API Reference](https://control.ros.org/humble/doc/api/index.html)
 
 ## Documentation