Re: doc: Improve wal_level and effective_wal_level GUC around logical replication

Few comments:

1)
+ Running read-only queries on a standby server.

Looks incomplete and disconnected from previous sentence.

2)
+ level used by the system. Namely, whether replica has been promoted to
+ logical (minimal never promotes).

We shall replace replica, logical, minimal with below
<literal>replica</literal>
<literal>logical</literal>
<literal>minimal</literal>

Also shall we add 'wal_level'? Otherwise, 'replica' on its own could
be understood as a replica server:

Namely, whether wal_level replica has been promoted to ....

3)
+ The <xref linkend="guc-effective-wal-level"/> parameter
reports the actual
+ level used by the system. Namely, whether replica has been promoted to
+ logical (minimal never promotes).
+ This parameter can only be set at server start.

"This" here is misleading. Does this refer to wal_level or effective_wal_level?

4)
Below that is <literal>minimal</literal>,

Shall we change "that" to <literal>replica</literal> to avoid any confusion?

thanks
Shveta