Use Date property (#872)

Co-authored-by: Michael Brown <[email protected]>

Sources/Scheduler.swift

@@ -699,7 +699,7 @@ public final class TestScheduler: DateScheduler {
  }
 
  /// Dequeues and executes all scheduled actions, leaving the scheduler's
- /// date at `Date.distantFuture()`.
+ /// date at `Date.distantFuture`.
  public func run() {
  advance(to: Date.distantFuture)
  }