pgsql: Fix outdated comment after removal of direct SSL fallback

Fix outdated comment after removal of direct SSL fallback

The option to fall back from direct SSL to negotiated SSL or a
plaintext connection was removed in commit fb5718f35f.

Discussion: https://www.postgresql.org/message-id/c82ad227-e049-4e18-8898-475a748b5a5a@iki.fi

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/5afebbe529abc896d4a3c5a092427c28f6be21ab

Modified Files
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src/interfaces/libpq/fe-connect.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)