Remove deprecated mimic parameter from ros2_control tag

[christophfroehlich]

A followup from #1256: Removing the deprecated mimic configuration via ros2_control section in the URDF.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.81%. Comparing base (02b20d2) to head (683c9f6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1553 +/- ## ========================================== + Coverage 87.80% 87.81% +0.01% ========================================== Files 102 102 Lines 8765 8732 -33 Branches 787 783 -4 ========================================== - Hits 7696 7668 -28 + Misses 791 789 -2 + Partials 278 275 -3 ``` | [Flag](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls) | `87.81% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls) | Coverage Δ | | |---|---|---| | [hardware\_interface/src/component\_parser.cpp](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553?src=pr&el=tree&filepath=hardware_interface%2Fsrc%2Fcomponent_parser.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls#diff-aGFyZHdhcmVfaW50ZXJmYWNlL3NyYy9jb21wb25lbnRfcGFyc2VyLmNwcA==) | `94.13% <100.00%> (+1.20%)` | :arrow_up: | | [hardware\_interface/test/test\_component\_parser.cpp](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553?src=pr&el=tree&filepath=hardware_interface%2Ftest%2Ftest_component_parser.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls#diff-aGFyZHdhcmVfaW50ZXJmYWNlL3Rlc3QvdGVzdF9jb21wb25lbnRfcGFyc2VyLmNwcA==) | `98.65% <ø> (-0.06%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1553/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls)

[mergify[bot]]

This pull request is in conflict. Could you fix it @christophfroehlich?