Fix msvc loss of data warning

[Blast545]

Summary

Attempt to fix the windows warning caused in the SimFactory code, reference:
https://build.osrfoundation.org/job/gz_launch-main-win/47/

It's complaining about an uint64 casted to protobuf::int32, so I think this PR should fix it. Don't fix it until checking win CI and validate if it actually fixes the problem.

cc: @Crola1702

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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[Blast545]

For reference, this warning appeared in the last pr-win job, see: https://build.osrfoundation.org/job/gz_launch-pr-win/44/
So, if it doesn't happen in the pr-win CI of this job, this PR should be good to be merged.