pgsql: Remove isolation test reindex-partitions

Remove isolation test reindex-partitions

The isolation test added by a6642b3 is proving to be unstable, as once
the first transaction holding a lock on the top-most partitioned table
or on a partition commits, the commit order of the follow-up DROP TABLE
and REINDEX could become reversed depending on the timing.

The only part of the test that could be entirely reliable is the one
using a SHARE lock, allowing REINDEX to commit first, but it is the
least interesting of the set.

Per buildfarm members rorqual and mylodon.

Discussion: https://postgr.es/m/E1kFSBj-00062c-Mu@gemulon.postgresql.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6785974287afa27221a49ae7202ea3d0695c0a84

Modified Files
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src/test/isolation/expected/reindex-partitions.out | 107 ---------------------
src/test/isolation/isolation_schedule | 1 -
src/test/isolation/specs/reindex-partitions.spec | 59 ------------
3 files changed, 167 deletions(-)