doc: Fix some grammar and inconsistencies

Michael Paquier <michael@paquier.xyz>

Commit: aad546bd0a51059aafe44e8c4a783afa1557d1d9
Author: Michael Paquier <michael@paquier.xyz>
Date: 2020-09-10T06:50:19Z
Releases: 14.0
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