Readd accidentally removed version constraint (#789)

Co-authored-by: Sander Kersten <[email protected]>

Author: spkersten

example/pubspec.yaml

@@ -11,7 +11,7 @@ dependencies:
   flutter:
     sdk: flutter
   flutter_lints: ^1.0.4
-  flutter_reactive_ble:
+  flutter_reactive_ble: ^5.2.0
   functional_data: ^1.0.0
   intl: ^0.17.0