pgsql: doc: improve NLS instruction wording

doc: improve NLS instruction wording

Reported-by: "Tang, Haiying"

Discussion: /messages/by-id/bbbccf7a3c2d436e85d45869d612fd6b@G08CNEXMBPEKD05.g08.fujitsu.local

Author: "Tang, Haiying"

Backpatch-through: 9.5

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/155bfbb543c220b3239ac8fc88e3de472f43e57a

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