bugfix: is_defaults() is a method, not property (microsoft#782)

Closes microsoft#781

Co-authored-by: Brian Kroth <[email protected]>

mlos_bench/mlos_bench/schedulers/base_scheduler.py

@@ -215,7 +215,7 @@ def schedule_trial(self, tunables: TunableGroups) -> None:
                 # prevented).
                 "optimizer": self.optimizer.name,
                 "repeat_i": repeat_i,
-                "is_defaults": tunables.is_defaults,
+                "is_defaults": tunables.is_defaults(),
                 **{
                     f"opt_{key}_{i}": val
                     for (i, opt_target) in enumerate(self.optimizer.targets.items())