chore: Return a well-defined value from setAutorun.

There is no documentation about what this function is supposed to do or what it
should return, so I'm just guessing it's a success boolean, so it should be
returning true.

src/platform/autorun_osx.cpp

@@ -38,6 +38,7 @@ bool Platform::setAutorun(bool on)
 
     state = on;
     autoRun.setValue("RunAtLoad", state);
+    return true;
 }
 
 bool Platform::getAutorun()