pgsql: Fix failure with pgperlcritic from the TAP test of synchronousr

Fix failure with pgperlcritic from the TAP test of synchronous replication

Oversight in 7d81bdc, which introduced a new routine in perl lacking a
return clause.  Per buildfarm member crake.

Backpatch down to 9.6 like its parent.

Reported-by: Andrew Dunstan
Discussion: https://postgr.es/m/16da29fa-d504-1380-7095-40de586dc038@2ndQuadrant.com
Backpatch-through: 9.6

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/24a6b6af650132094f7f8547458a3835cf01be7f

Modified Files
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src/test/recovery/t/007_sync_rep.pl | 1 +
1 file changed, 1 insertion(+)