Fix goal_checker_plugin parameter format

[ipa-kut]

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Basic Info

Info	Please fill out this column
Tickets	#3136
Primary OS tested on	Ubuntu 22.04/20.04
Robotic platform tested on	Multi robot gazebo simulation

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Description of contribution in a few bullet points

• Fixed goal_checker_plugin parameter format. See nav2_bringup: Multi robot sim - goal_checker_plugins parameters have wrong format #3136

Description of documentation updates required from your changes

None

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Future work that may be required in bullet points

None

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[mergify]

@ipa-kut, all pull requests must be targeted towards the main development branch.
Once merged into main, it is possible to backport to @humble, but it must be in main
to have these changes reflected into new distributions.

[mergify]

@ipa-kut, please properly fill in PR template in the future. @SteveMacenski, use this instead.

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists