pgsql: Re-adhere to policy of no more than 20 tests per parallelgroup.

Re-adhere to policy of no more than 20 tests per parallel group.

As explained at the head of parallel_schedule, we place an arbitrary limit
of 20 test cases per parallel group.  Commit c7a9fa399 overlooked this.

Least messy solution seems to be to move the "comments" test to the next
group, since it doesn't really belong in a group of datatype tests anyway.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/7d3957e53ebf26fc8d72dee1dacc2c827cc07caa

Modified Files
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src/test/regress/parallel_schedule | 4 ++--
src/test/regress/serial_schedule   | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)