pgsql: Docs: tidy up various usages of the productname tag

Docs: tidy up various usages of the productname tag

This tries to bring a bit more consistency to the use of the <productname>
tag in the documents. This fixes a couple of mistakes with our own
product. We definitely should be consistently calling that PostgreSQL
when we're referring to the modern-day version of the software.

This also tidies up a couple of inconsistencies with the case of other
product names, namely Emacs and Python. We also get rid of some incorrect
usages of <productname> and replace them with <literal>.

Many of these mistakes exist in the back branches, but they don't quite
seem critical enough to warrant fixing them in prior versions at this
stage.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fdc18ea23b393d4a34c78b94ad3fcaf547e74959

Modified Files
--------------
doc/src/sgml/catalogs.sgml | 2 +-
doc/src/sgml/client-auth.sgml | 4 ++--
doc/src/sgml/ecpg.sgml | 2 +-
doc/src/sgml/install-windows.sgml | 2 +-
doc/src/sgml/sources.sgml | 2 +-
5 files changed, 6 insertions(+), 6 deletions(-)