Fix comments to clarify that an absolute path does not work for OrchardCore_Media__AssetsPaths

[rjpowers10]

Fixes #16263

[Piedone]

Looks good, but let's wait for the triage of the issue on Thursday to see if updating the docs is indeed the best next step.

[sebastienros]

Thanks, we updated the suggested sentence to remove the "must" work which was confusing.

[sebastienros]

@rjpowers10 we just merged your PR and are having a discussion about this action. Would you have preferred us to comment on your changes and let you review them or do you prefer what we did and just went on with merging the changes we did directly to prevent back and forth?

[rjpowers10]

@sebastienros with a simple docs change like this I think it's fine to just make the change directly. No need to complicate things.