Remove turbodbc tests #5629
Description
Testing of turbodbc is adversely affecting the versions of numpy that we can test. Due to its complex build process (which now has some new dependencies), we can't update to the latest version of turbodbc without a non-trivial amount of additional work. Our testing of turbodbc has always been "aspirational" given our bespoke build process around it only for our own testing purposes. Customers should still be able to use turbodbc with Deephaven, we just won't be testing our custom (or any) build of turbodbc.