Move spec_version to shared

src/shared.py

@@ -53,4 +53,4 @@ image_size = (200 * scale_factor, 300 * scale_factor)
 win = None
 importer = None
 store = None
-spec_version = 1.5  # The version of the game_id.json spec
+spec_version = 2.0  # The version of the game_id.json spec

src/window.py

@@ -74,9 +74,6 @@ class CartridgesWindow(Adw.ApplicationWindow):
     details_view_game_cover = None
     sort_state = "a-z"
 
-    # The version of the game_id.json spec
-    spec_version = 2.0
-
     def __init__(self, **kwargs):
         super().__init__(**kwargs)