pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "

pgsql: Doc: copy-edit the introductory para for the pg_class catalog.

Doc: copy-edit the introductory para for the pg_class catalog. The previous wording had a faint archaic whiff to it, and more importantly used "catalogs" as a verb, which while cutely self-referential seems likely to provoke confusion in this particular context. Also consistently use "kind" not "