Fix examples and files with invalid extra diffuse values

[PixnBits]

🦟 Bug fix

Fixes #

Summary

Following the Building Your Own Robot tutorial I encountered an error when adding the caster wheel:

pixnbits@n2023ubu:~/my-robots$ gz sim tutorial.sdf 
Error [Param.cc:1288] Error Code 34: Msg: The value <diffuse>0.0 1 0.0 1 1</diffuse> is invalid.
[Err] [Server.cc:198] Error Code 9: [/sdf/world[@name="car_world"]/model[@name="vehicle_blue"]/link[@name="caster"]/visual[@name="visual"]/material/diffuse:/home/pixnbits/my-robots/tutorial.sdf:L263]: Msg: Error reading element <diffuse>

It appears an extra 1 is at the end, removing it allows Gazebo to run.
I used grep -rl "<diffuse>0.0 1 0.0 1 1</diffuse>" to find instances where this was present and removed the trailing 1 from them.

I've tested this by attempting to run Gazeebo with the SDF files, both after and before the changes of this PR (though citadel/tutorials/sensors/sensor_tutorial.sdf appears to be unusable either way). E.g.:

Error [Param.cc:1288] Error Code 34: Msg: The value <diffuse>0.0 1 0.0 1 1</diffuse> is invalid.
[Err] [Server.cc:198] Error Code 9: [/sdf/world[@name="sensor_world"]/model[@name="vehicle_blue"]/link[@name="caster"]/visual[@name="visual"]/material/diffuse:/home/pixnbits/projects/docs-1/dome/tutorials/sensors/sensor_tutorial.sdf:L320]: Msg: Error reading element <diffuse>

It might be useful to add a test to use gz to parse the SDF files, but I'm not sure where the test setup is for this repository (I don't want to ignore it and cause unintended maintenance issues 😅)

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)
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[PixnBits]

Ah! FWIW it appears this was fixed in newer documentation via #161

[iche033]

thanks for the fix