pgsql: Use Test::Builder::todo_start(), replacing $::TODO.

Use Test::Builder::todo_start(), replacing $::TODO.

Some pre-2017 Test::More versions need perfect $Test::Builder::Level
maintenance to find the variable.  Buildfarm member snapper reported an
overall failure that the file intended to hide via the TODO construct.
That trouble was reachable in v11 and v10.  For later branches, this
serves as defense in depth.  Back-patch to v10 (all supported versions).

Discussion: https://postgr.es/m/20220202055556.GB2745933@rfd.leadboat.com

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2373429975ac28307583f49416f8943e7c04c8ff

Modified Files
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src/bin/pgbench/t/023_cic_2pc.pl | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)