pgsql: Stabilize regression test result.

Stabilize regression test result.

If random() returns a result sufficiently close to zero, float8out
switches to scientific notation, breaking this test case's expectation
that the output should look like '0.xxxxxxxxx'.  Casting to numeric
should fix that.  Per buildfarm member pogona.

Discussion: https://postgr.es/m/20180324212502.wt4serghfidge2on@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/038a2ed1392363a59adeee4e86d848ca74ce39c5

Modified Files
--------------
src/test/regress/expected/create_procedure.out | 2 +-
src/test/regress/sql/create_procedure.sql      | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)