Remove absolute path in new Fuchsia SDK based runner target dependency. (#8888)

Only ran into this as I was wiring up the bots to build the new targets.

shell/platform/fuchsia/dart-pkg/zircon/sdk_ext/handle_waiter.h

@@ -8,7 +8,7 @@
 #include <lib/async/cpp/wait.h>
 #include <lib/zx/handle.h>
 
-#include "/Users/chinmaygarde/VersionControlled/engine/src/flutter/fml/memory/ref_counted.h"
+#include "flutter/fml/memory/ref_counted.h"
 #include "third_party/tonic/dart_wrappable.h"
 
 namespace tonic {