doc: Fix some grammar and inconsistencies

Michael Paquier <michael@paquier.xyz>

Commit: d56d33052183ca57c5a91e16f8c7713903cc6fee
Author: Michael Paquier <michael@paquier.xyz>
Date: 2020-09-10T06:50:54Z
Releases: 10.15
doc: Fix some grammar and inconsistencies

Some comments are fixed while on it.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20200818171702.GK17022@telsasoft.com
Backpatch-through: 9.6

Files

Documentation touched

Discussion