pgsql: doc: correct syntax of pgtrgm examples in older releases

doc: correct syntax of pgtrgm examples in older releases

Reported-by: Liudmila Mantrova

Discussion: /messages/by-id/ded40ecb-557e-8c50-7d58-69f4b5226664@postgrespro.ru

Backpatch-through: 9.6 and 10 only

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/c2ea62f58575045bd85156581f55b57067f33fd8

Modified Files
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doc/src/sgml/pgtrgm.sgml | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)