pgsql: Remove pg_regress' never-documented "ignore" feature.

Remove pg_regress' never-documented "ignore" feature.

We aren't using this anymore in the wake of commit 09d517773,
so delete it.  We can always revert this if some future use
emerges, but I think our standards for test quality are now
high enough that that will never happen.

Discussion: https://postgr.es/m/4173840.1673290336@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bd8d453e9b5f8b632a400a9e796fc041aed76d82

Modified Files
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src/test/regress/pg_regress.c | 60 ++++---------------------------------------
1 file changed, 5 insertions(+), 55 deletions(-)