Follow-up from "Fix some QMT tests"

The following discussion from !94 (merged) should be addressed:

Using testfiledb_key directly in the json files used in the tests here does not work, I get

ERROR:  Failed to validate options! Found 2 errors:
/usera/jonesc/LHCb/stack/Master/LHCb/InstallArea/x86_64_v3-el9-gcc13+detdesc-opt+g/python/GaudiConf/LbExec/cli_utils.py:217: UserWarning: Callable lines_maker was excluded from schema since JSON schema has no equivalent type.
  error["loc"][0], function.OptionsClass.schema()["properties"], n=1
 * extra fields not permitted: 'testfiledb_key' 
 * 'input_files' is required when input_type=ROOT