pgsql: Don't install postmaster symlink anymore

Don't install postmaster symlink anymore

This has long been deprecated.  Some of the build systems didn't even
install it.

Also remove man page.

Reviewed-by: Karl O. Pinc <kop@karlpinc.com>
Discussion: https://www.postgresql.org/message-id/flat/ece84b69-8f94-8b88-925f-64207cb3a2f0@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/37e267335068059ac9bd4ec5d06b493afb4b73e8

Modified Files
--------------
doc/src/sgml/ref/allfiles.sgml   |  1 -
doc/src/sgml/ref/postmaster.sgml | 44 ----------------------------------------
doc/src/sgml/reference.sgml      |  1 -
src/backend/Makefile             |  8 +-------
4 files changed, 1 insertion(+), 53 deletions(-)