TrackerCrawler: Fix up prototype for ::finished.
TrackerCrawler: Fix up prototype for ::finished.

The ::finished signal changed parameters some time ago, but the function
prototype in the class struct didn't.

hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker