tests/qtest/migration-test: Remove duplicated test_postcopy from the test plan

test_postcopy() is currently run twice - which is just a waste of resources
and time. The commit d1a27b169b2d that introduced the duplicate talked about
renaming the "postcopy/unix" test, but apparently it forgot to remove the
old entry. Let's do that now.

Fixes: d1a27b169b ("tests: Add postcopy tls migration test")
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220819053802.296584-5-thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20220822165608.2980552-6-alex.bennee@linaro.org>

tests/qtest/migration-test.c

@@ -2461,7 +2461,6 @@ int main(int argc, char **argv)
     module_call_init(MODULE_INIT_QOM);
 
     if (has_uffd) {
-        qtest_add_func("/migration/postcopy/unix", test_postcopy);
         qtest_add_func("/migration/postcopy/plain", test_postcopy);
         qtest_add_func("/migration/postcopy/recovery/plain",
                        test_postcopy_recovery);