pgsql: Relax check for return value from second call of pg_strnxfrm().

Relax check for return value from second call of pg_strnxfrm().

strxfrm() is not guaranteed to return the exact number of bytes needed
to store the result; it may return a higher value.

Discussion: https://postgr.es/m/32f85d88d1f64395abfe5a10dd97a62a4d3474ce.camel@j-davis.com
Reviewed-by: Heikki Linnakangas
Backpatch-through: 16

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/10fdc67f81972a03eee928a3b0ae226a78243fad

Modified Files
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src/backend/access/hash/hashfunc.c |  8 ++++++--
src/backend/utils/adt/pg_locale.c  | 12 ++++++------
src/backend/utils/adt/varchar.c    |  8 ++++++--
3 files changed, 18 insertions(+), 10 deletions(-)