pgsql: Doc: tweak installation doc edits made by commit 76c2af926.

Doc: tweak installation doc edits made by commit 76c2af926.

We don't consider that building with MinGW is deprecated,
so adjust some places that gave that impression.
Per discussion with Peter Eisentraut.

Discussion: /messages/by-id/4a023388-8652-fea0-a0b4-35ad5e734e9a@2ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71a01086603cc3a27c0d6ae60228aeb13c32d359

Modified Files
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doc/src/sgml/installation.sgml | 15 ++++++++-------
doc/src/sgml/standalone-install.xml | 8 ++++++++
2 files changed, 16 insertions(+), 7 deletions(-)