doc: Clarify that \d and \d+ output lists are illustrative, not exhaustive.

doc: Clarify that \d and \d+ output lists are illustrative, not exhaustive.

The psql documentation for the \d and \d+ meta-commands lists objects
that may be shown, but previously the wording could be read as exhaustive
even though additional objects can also appear in the output.

This commit clarifies the description by adding phrasing such as "for example"
or "such as", making it clear that the listed objects are illustrative
rather than a complete list. While the change is small, it helps avoid
potential user confusion.

As this is a documentation clarification rather than a bug fix,
it is not backpatched.

Author: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAHut+Pt1DBtaUqfJftkkaQLJJJenYJBtb6Ec6s6vu82KEMh46A@mail.gmail.com