Summary

• Remove the unused MACHINE_VIDEO flag on the Celebris
• Fix the min. voltages on both Siemens machines
• Remove the unused MACHINE_GAMEPORT flag on the OP47, along with the inaccurate internal note

Checklist

• Closes #xxx
• I have tested my changes locally and validated that the functionality works as intended
• I have discussed this with core contributors already
• This pull request requires changes to the ROM set
  • I have opened a roms pull request - https://github.com/86Box/roms/pull/changeme/
• This pull request requires changes to the asset set
  • I have opened an assets pull request - https://github.com/86Box/assets/pull/changeme/

References

N/A