pgsql: Remove unnecessary inclusion of libpq into pg_regress --- overly

Log Message:
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Remove unnecessary inclusion of libpq into pg_regress --- overly
enthusiastic copy and paste ...

Modified Files:
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pgsql/src/test/regress:
GNUmakefile (r1.58 -> r1.59)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/GNUmakefile.diff?r1=1.58&r2=1.59)