DAOS-9576 test: remove path to ddb src in ut

[johannlombardi]

required_src was added to avoid conflicts on the file during feature development. It is not necessary any longer (and wrong since ddb has moved from src to src/utils now).

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[github-actions]

Errors are Unable to load ticket data
https://daosio.atlassian.net/browse/DAOS-9576

[daltonbohning]

ddb unit tests are running now:
https://build.hpdd.intel.com/job/daos-stack/job/daos/job/PR-14238/1/testReport/UTEST_ddb/