pgsql: Fix error message typo introduced 691d79a07933. - Mailing list pgsql-committers

Fix error message typo introduced 691d79a07933.

Reported-By: Michael Paquier
Discussion: https://postgr.es/m/20181101003405.GB1727@paquier.xyz
Backpatch: 9.4-, like the previous commit

Branch
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REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b0fa768c61b329b72e882b7923eccb249c26d74c

Modified Files
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src/backend/replication/slot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)