Fix build for Python versions <3.9 (#855)

Co-authored-by: Andrei Fominykh <afominykh@topcon.com>

scripts/meta.py

@@ -49,7 +49,7 @@ class Main(App):
         for path in self.args.input[0]:
             with open(path, mode="r") as file:
                 dict = json.loads(file.read())
-                full |= dict
+                full.update(dict)
 
         print(json.dumps(full, indent=4))
         return 0