Fixed DockerFile build warning

[JatinPatil2003]

---

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#4461
Primary OS tested on	Docker
Does this PR contain AI generated software?	No

---

Description of contribution in a few bullet points

• fixed Dockerfile for the empty continuation line warning

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

[codecov[bot]]

Codecov Report

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

see 1 file with indirect coverage changes