pgsql: Avoid using ambiguous word "positive" in error message.

Avoid using ambiguous word "positive" in error message.

There are two identical error messages about valid value of modulus for
hash partition, in PostgreSQL source code. Commit 0e1275fb07 improved
only one of them so that ambiguous word "positive" was avoided there,
and forgot to improve the other. This commit improves the other.
Which would reduce translator burden.

Back-pach to v11 where the error message exists.

Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/20210819.170315.1413060634876301811.horikyota.ntt@gmail.com

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f53ceaea8a1da638a5c68a09676c67e90b7de870

Modified Files
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src/backend/parser/parse_utilcmd.c         | 2 +-
src/test/regress/expected/alter_table.out  | 2 +-
src/test/regress/expected/create_table.out | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)