Update particle emitter tutorial

[iche033]

🦟 Bug fix

Summary

Fixed the tutorial gist world file and moved it to gz-sim (https://github.com/gazebosim/gazebo_test_cases/issues/1254#issuecomment-2323123365). The world file has one syntax error and it's also using outdated ignition syntaxes. Moving it to gz-sim so it's easier spot and maintain issues like these.

Checklist

• [x] Signed all commits for DCO
• [ ] Added tests
• [x] 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.

[ahcorde]

@osrf-jenkins run tests please!