Changed step_size to 0.5 in collision checker

[afifswaidan]

---

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#3151
Primary OS tested on	Ubuntu 22.04.01
Robotic platform tested on	None

---

Description of contribution in a few bullet points

• This PR is to change step_size to 0.5 instead of 0.1 in the footprint collision checker as discussed in Update index.rst docs.nav2.org#382 (comment)

---

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]

@afifswaidan, 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