pgsql: Don't link pg_isolation_regress with libpq

Don't link pg_isolation_regress with libpq

It's not necessary and can only create confusion about which libpq
installation should be used.

Also remove some dead code from the makefile that was apparently
copied from elsewhere.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/36a1a8c33d0d400b246dec8395990725b98801b7

Modified Files
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src/test/isolation/Makefile |    9 ++-------
1 files changed, 2 insertions(+), 7 deletions(-)