Issue #1929420 by krlucas, kay_v, quietone, seiplax, floydm, alexpott, mlncn,...

Issue #1929420 by krlucas, kay_v, quietone, seiplax, floydm, alexpott, mlncn, nlisgo, gulab.bisht, scor, longwave, pameeela: $account->getDisplayName() should be used when outputing username in RDF module

(cherry picked from commit 4e7ba766)