Change mocap_msgs to mocap4r2_msgs

[incebellipipo]

Hi all,

A similar pull request from mocap4r2_msgs to mocap_msgs was merged previously. Thus, I am not certain if this pull request is relevant. But when we try to install the package, we encounter a couple of problems. First, there is no 'main' or 'master' branch anymore for the mocap4r2_msgs package, it is 'rolling'. Second, the name is mocap4r2_msgs, not mocap_msgs. So, this pull request changes mocap_msgs to mocap4r2_msgs.

[fmrico]

Hi @incebellipipo

These changes are related to our intention to create packages for different distros. The change of the name is related to this: ros/rosdistro#39475 (comment). The change of the name of the main branch to rolling emphasizes using rolling to develop new features. Following this rule, as soon as a new distro appears, we could directly branch to that distro to create the packages.

I will accept this PR, even with the test failing. The failure is related to the CI so that I will fix it.

Thanks for your PR ;)

[fmrico]

Actually, I will change the main branch to rolling soon, so stay tuned.