fix(projectsADM): fix cache issue in getSingleProjectADM (#2054)

Author: mpro7

webapi/src/main/scala/org/knora/webapi/responders/admin/ProjectsResponderADM.scala

@@ -249,6 +249,8 @@ class ProjectsResponderADM(responderData: ResponderData) extends Responder(respo
             log.debug("getSingleProjectADM - could not retrieve project: {}", identifier.value)
           }
 
+        _ = storeManager ? CacheServiceFlushDB(KnoraSystemInstances.Users.SystemUser)
+
       } yield maybeProjectADM
     }