tor-config: Expand NoProjectDirs error message
I considered whether we should use the "hint" system but I decided against, because:
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This happens on Android and there people aren't running the arti CLI, but using our API, and they are likely not to use the hint system.
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This extra text containing speculations is taking the place of real information that ought to be provided but isn't due to a poor upstream API in
directories
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This error is rare in normally configured systems so making it long is fine.
Assigning review to @gabi-250 since she did the previous two MRs in this area.