Speed up running tests when compiled with DUCKDB_BUILD=Debug

[JelteF]

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Without this change it takes more than a minute to run make installcheck on my machine if I enable DUCKDB_BUILD=Debug. Because both of these tests take more than thirty seconds. After this change both execute in less than 2 seconds. Especially the first test taking so long is confusing, because it seems like the tests are not working.