improve more permissions-related error messages

This is intended as a follow-up to de4d456 [0].  I noticed that c3afe8c
introduced another "must have privileges" error message that I think should
be adjusted to use the new style introduced in de4d456.  І've attached a
small patch for this.

While looking around for other such error messages, I found a few dozen
"must be superuser" errors that might be improved with the new style.  If
folks feel this is worthwhile, I'll put together a patch.

[0] https://postgr.es/m/20230126002251.GA1506128%40nathanxps13

-- 
Nathan Bossart
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