Hi,
There's two main ways you can do this:
1. You can message the Magic Rules Manager Eli Shiffrin via his Twitter account -
https://twitter.com/EliShffrn Eli is in charge of maintaining the Gatherer rulings, so he would be the most direct source.
2. You can message me (Nathan Long) via JudgeApps, and I'll pass them along to Eli.
Note that Gatherer isn't updated constantly - it's generally only updated with set releases (and the update for War of the Spark is likely already locked in place), so it may take some time for a ruling to be corrected or updated.
Gatherer rulings are intended to always be accurate rulings. Judges should accept them as an official clarification of how cards work. Rulings may not account for edge cases (in which case, determine why the edge case makes it not applicable), but if a ruling appears to be factually inaccurate, inform us and we'll fix it. Telling a player or another judge to simply not trust Gatherer rulings is not correct.
Nathan Long
Magic Rules NetRep