pgsql: postgres_fdw: Revert unstable tests for postgres_fdw.application

postgres_fdw: Revert unstable tests for postgres_fdw.application_name.

Commit 449ab63505 added the tests that check that postgres_fdw.application_name
GUC works as expected. But they were unstable and caused some buildfarm
members to report the failure. This commit reverts those unstable tests.

Reported-by: Tom Lane as per buildfarm
Discussion: https://postgr.es/m/3220909.1631054766@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/98dbef90eb29b13079ba3bd260b3c5818904ee86

Modified Files
--------------
contrib/postgres_fdw/expected/postgres_fdw.out | 79 --------------------------
contrib/postgres_fdw/sql/postgres_fdw.sql      | 39 -------------
2 files changed, 118 deletions(-)