Fix some typos, grammar and style in docs and comments

Michael Paquier <michael@paquier.xyz>

Commit: 3b2af88788e1e136bcde78b74ff7387b0c58488a
Author: Michael Paquier <michael@paquier.xyz>
Date: 2021-02-24T07:14:00Z
Releases: 12.7
Fix some typos, grammar and style in docs and comments

The portions fixing the documentation are backpatched where needed.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20210210235557.GQ20012@telsasoft.com
backpatch-through: 9.6

Files

Documentation touched

Discussion