Adjust dblp author query to be compatible with older qlever version

[tholzheim]

https://github.com/WolfgangFahl/pyCEURmake/blob/e1a3ac0b8f2e3fddbe4573ad9142b1bcbd6243e8/ceurws/resources/queries/dblp.yaml#L41 is a feature that is only supported by a newer version of qlever thus does currently not work on our endpoint