Update flet dependency to use custom git ref

Switched flet dependency from a fixed version to a git reference pointing to the 'rive-0-14-0' branch. This allows using the latest changes from that branch instead of the published version.

{{cookiecutter.out_dir}}/pubspec.yaml

@@ -32,13 +32,13 @@ dependencies:
   window_manager: ^0.5.1
   
 dependency_overrides:
-  flet: 0.80.2
+  # flet: 0.80.2
 
-  # flet:
-  #   git:
-  #     path: packages/flet
-  #     ref: main
-  #     url: https://github.com/flet-dev/flet.git
+  flet:
+    git:
+      path: packages/flet
+      ref: rive-0-14-0
+      url: https://github.com/flet-dev/flet.git
 
   serious_python:
     git: