Update pubspec.yaml

Update version to 1.5.2

Author: Woolloff

pubspec.yaml

@@ -1,6 +1,6 @@
 name: responsive_framework
 description: Easily make Flutter apps responsive. Automatically adapt UI to different screen sizes. Responsiveness made simple.
-version: 1.5.1
+version: 1.5.2
 homepage: https://codelessly.com
 repository: https://github.com/Codelessly/ResponsiveFramework
 documentation: https://github.com/Codelessly/ResponsiveFramework
@@ -19,4 +19,4 @@ dev_dependencies:
     sdk: flutter
   flutter_lints: ^4.0.0
 
-flutter:
+flutter: