RE: [PGdocs] fix description for handling pf non-ASCII characters

Dear Tom,

> No, I'm pretty sure you're mistaken.  It's been a long time since
> high school English, but the way I think this works is that "that"
> introduces a restrictive clause, which narrows the scope of what
> you are saying.  That is, you say "that" when you want to talk
> about only the bytes of the string that aren't ASCII.  But "which"
> introduces a non-restrictive clause that adds information or
> commentary.  If you say "bytes of the string which are not ASCII",
> you are effectively making a side assertion that no byte of the
> string is ASCII.  Which is not the meaning you want here.
> 
> A smell test that works for native speakers (not sure how helpful
> it is for others) is: if the sentence would read well with commas
> or parens added before and after the clause, then it's probably
> non-restrictive and should use "which".  If it looks wrong that way
> then it's a restrictive clause and should use "that".

Thanks for giving your opinion. The suggestion is quite helpful for me,
non-native speaker. If you check my patch [1] I'm very happy.

[1]: https://www.postgresql.org/message-id/TYAPR01MB58663EB061888B2715A39217F5C2A%40TYAPR01MB5866.jpnprd01.prod.outlook.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED