pgsql: Remove gratuitous references to postmaster program

Remove gratuitous references to postmaster program

"postgres" has long been officially preferred over "postmaster" as the
name of the program to invoke to run the server.  Some example scripts
and code comments still used the latter.  Change those.

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/81266442fbcb19ec184134f0a256207f05026520

Modified Files
--------------
contrib/start-scripts/freebsd | 10 +++++-----
contrib/start-scripts/linux   | 10 +++++-----
src/port/path.c               |  2 +-
3 files changed, 11 insertions(+), 11 deletions(-)