Do not use language tag on username when fetching user by name

src/main/java/cz/cvut/kbss/analysis/dao/UserDao.java

@@ -37,7 +37,7 @@ public Optional<User> findByUsername(String username) {
                                     type)
                             .setParameter("type", typeUri)
                             .setParameter("hasUsername", URI.create(Vocabulary.s_p_username))
-                            .setParameter("username", username, config.getLanguage())
+                            .setParameter("username", username)
                             .getSingleResult());
         } catch (NoResultException e) {
             return Optional.empty();