Small fixes to gz headers

[scpeters]

🦟 Bug fix

Fixes two small issues with ign -> gz header backport.

Summary

I noticed two small issues with the ign -> gz header conversion that are fixed here:

• 6be22d4: one of the headers was still using an ignition/ header, which is easily fixed.
• a37883a: the auto-generated components.hh header was still being installed to ignition/gazebo/components.hh; this corrects it to gz/sim/components.hh.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #1985 (816594d) into ign-gazebo3 (2a12514) will not change coverage.
The diff coverage is n/a.

❗ Current head 816594d differs from pull request most recent head a37883a. Consider uploading reports for the commit a37883a to get more accurate results

@@             Coverage Diff              @@
##           ign-gazebo3    #1985   +/-   ##
============================================
  Coverage        78.03%   78.03%           
============================================
  Files              255      255           
  Lines            15082    15082           
============================================
  Hits             11769    11769           
  Misses            3313     3313           

Impacted Files	Coverage Δ
include/gz/sim/gui/TmpIface.hh	0.00% <ø> (ø)