pgsql: Temporarily(?) remove BRIN isolation test.

Temporarily(?) remove BRIN isolation test.

Commit 2834855cb added a not-very-carefully-thought-out isolation test
to check a BRIN index bug fix. The test depended on the availability
of the pageinspect contrib module, which meant it did not work in
several common testing scenarios such as "make check-world". It's not
clear whether we want a core test depending on a contrib module like
that, but in any case, failing to deal with the possibility that the
module isn't present in the installation-under-test is not acceptable.

Remove that test pending some better solution.

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/0ae43b6a631ce8507ef4bd68ce297853a8986fe8

Modified Files
--------------
src/test/isolation/expected/brin-1.out | 39 ----------------------------
src/test/isolation/isolation_schedule | 1 -
src/test/isolation/specs/brin-1.spec | 44 --------------------------------
3 files changed, 84 deletions(-)