⚠️ Gazebo 11 will be required by robotology-superbuild from v2021.11 distro release

[traversaro]

Hi everyone,
as discussed in robotology/robotology-superbuild#812, from v2021.11 distro release, the robotology-superbuild will stop supporting Gazebo 9 or 10, and will require users to have installed Gazebo 11 to use the ROBOTOLOGY_USES_GAZEBO option.

The affected repos will be mainly icub-models and gazebo-yarp-plugins. In particular, the compilation of the plugins will not be tested anymore against Gazebo 9, and all SDF models will switch to use SDF version 1.7 .

The v2021.08 distro release will be the last one supporting Gazebo 9 or 10.