[LifecycleManagerClient] clean set_initial_pose and navigate_to_pose

[doisyg]

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Basic Info

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Ticket(s) this addresses
Primary OS tested on	Ubuntu
Robotic platform tested on	Dexory robot

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Description of contribution in a few bullet points

I was looking at nav2_lifecycle_manager/include/nav2_lifecycle_manager/lifecycle_manager_client.hpp and noticed 2 methods that do not seem to be used anywhere: set_initial_pose and navigate_to_pose. I guess they can be removed ?

For Maintainers:

• [ ] Check that any new parameters added are updated in docs.nav2.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

[SteveMacenski]

I have no idea why our static analysis tools didn't call this out, thanks!