pgsql: Fix incorrect option name in usage screen

Fix incorrect option name in usage screen

The usage screen incorrectly refered to the --docs option as --sgml.
Backpatch down to v17 where this script was introduced.

Author: Daniel Gustafsson <daniel@yesql.se>
Discussion: /messages/by-id/20250729.135638.1148639539103758555.horikyota.ntt@gmail.com
Backpatch-through: 17

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e5393fc2e4539bfd50e62ad4959c2712cb6505ce

Modified Files
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src/backend/utils/activity/generate-wait_event_types.pl | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)