Fix malformed XML in cached ik kinematics

[mini-1235]

Description

Hi, after ros/pluginlib#165 is merged, we can list all plugins by using

ros2 plugin list

However, I encountered an error when listing moveit's plugins due to the malformed XML

moveit_kinematics:
Traceback (most recent call last):
  File "/opt/ros/rolling/bin/ros2", line 33, in <module>
    sys.exit(load_entry_point('ros2cli==0.40.1', 'console_scripts', 'ros2')())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/ros/rolling/lib/python3.12/site-packages/ros2cli/cli.py", line 91, in main
    rc = extension.main(parser=parser, args=args)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/pluginlib_ws/build/ros2plugin/ros2plugin/command/plugin.py", line 37, in main
    return extension.main(args=args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/pluginlib_ws/build/ros2plugin/ros2plugin/verb/list.py", line 69, in main
    tree = ET.parse(plugin_xml)
           ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/xml/etree/ElementTree.py", line 1204, in parse
    tree.parse(source, parser)
  File "/usr/lib/python3.12/xml/etree/ElementTree.py", line 569, in parse
    self._root = parser._parse_whole(source)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 2, column 129

This PR fixes the issue

moveit_kinematics:
        Plugin(name='kdl_kinematics_plugin/KDLKinematicsPlugin', type='kdl_kinematics_plugin::KDLKinematicsPlugin', base='kinematics::KinematicsBase')
        Plugin(name='srv_kinematics_plugin/SrvKinematicsPlugin', type='srv_kinematics_plugin::SrvKinematicsPlugin', base='kinematics::KinematicsBase')
        Plugin(name='cached_ik_kinematics_plugin/CachedKDLKinematicsPlugin', type='cached_ik_kinematics_plugin::CachedIKKinematicsPlugin<kdl_kinematics_plugin::KDLKinematicsPlugin>', base='kinematics::KinematicsBase')
        Plugin(name='cached_ik_kinematics_plugin/CachedSrvKinematicsPlugin', type='cached_ik_kinematics_plugin::CachedIKKinematicsPlugin<srv_kinematics_plugin::SrvKinematicsPlugin>', base='kinematics::KinematicsBase')
moveit_planners_chomp:
        Plugin(name='chomp_interface/CHOMPPlanner', type='chomp_interface::CHOMPPlannerManager', base='planning_interface::PlannerManager')

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[mini-1235]

@nbbrooks Can you take a look on this PR :)