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