Disable setting particle emitter color range

[iche033]

🦟 Bug fix

Related issue: #902

Summary

Setting the particle emitter color range causes particles to appear black instead of actually changing the color of the particles to the range specified. The problem is that is affecting particle emitters that have also a material set (via SetMaterial) - the material diffuse color is overriden and results in black particles.

This PR just disables that function for now, see more details in #902

Test with gz sim -v 4 particle_emitter.sdf. With these changes, you should now see that the particles on the left side of the scene appears red (the intended color specified in the <material> tag) instead of black with flickering red.

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 #903 (69b4055) into gz-rendering7 (6fa1fc1) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 69b4055 differs from pull request most recent head 5bd43c9. Consider uploading reports for the commit 5bd43c9 to get more accurate results

@@                Coverage Diff                @@
##           gz-rendering7     #903      +/-   ##
=================================================
- Coverage          77.23%   77.22%   -0.01%     
=================================================
  Files                170      170              
  Lines              14738    14721      -17     
=================================================
- Hits               11383    11369      -14     
+ Misses              3355     3352       -3     

Files Changed	Coverage Δ
ogre2/src/Ogre2ParticleEmitter.cc	77.59% <100.00%> (-0.41%)	⬇️

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