pgsql: Remove obsolete documentation build tools for Windows

Remove obsolete documentation build tools for Windows

The scripts and instructions have been nonfunctional at least since
PostgreSQL 10 (commit 510074f9f0131a04322d6a3d2a51c87e6db243f9) and
nobody has stepped up to fix them.  So right now just remove them until
someone wants to resurrect them.

Discussion: https://www.postgresql.org/message-id/flat/B74C0219-6BA9-46E1-A524-5B9E8CD3BDB3%40yesql.se

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1f4ec8945967a75f711d721860752985624a0957

Modified Files
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doc/src/sgml/install-windows.sgml |  47 ---------------
src/tools/msvc/README             |   1 -
src/tools/msvc/builddoc.bat       |   7 ---
src/tools/msvc/builddoc.pl        | 124 --------------------------------------
4 files changed, 179 deletions(-)