[DOCS] pg_restore option data-only and section=data

Hello,pgsql-docs

I'd like to propose improving following the description of PostgerSQL
documentation.

https://www.postgresql.org/docs/9.6/static/app-pgrestore.html

------------------------------------------------------------------------
This option is similar to, but for historical reasons not identical to,
specifying --section=data.
------------------------------------------------------------------------

I think this description is ambiguous for postgresql user(not Hacker).
In fact, my customer inquired our support "What is the difference
between  '--section=data' and --data-only ?".

I've read this git comment.

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=4317e0246c645f60c39e6572644cff1cb03b4c65
------------------------------------------------------------------------
Rewrite --section option to decouple it from --schema-only/--data-only.
------------------------------------------------------------------------

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=5110a96992e508b220a7a6ab303b0501c4237b4a
------------------------------------------------------------------------
This fixes an undesirable inconsistency between
the meanings of "--data-only" and "--section=data"
------------------------------------------------------------------------

Now,there is no difference  between '--section=data' and --data-only "
from the view point of user .Because they make same output.
(But internal procedure is different.)


So how about  changing description from

"This option is similar to, but for historical reasons not identical
to, specifying --section=data."

to

"This option makes same result which --section=data makes, but
internal procedure is different for historical reasons"


Regard Kenichiro Tanaka