chore: Switch copyright to DFINITY Stiftung (#337)

IP needs to be owned by the parent entity, i.e. DFINITY Stiftung, and
not by the subsidiary (DFINITY LLC).

LICENSE

@@ -187,7 +187,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2022 DFINITY LLC.
+   Copyright 2022 DFINITY Stiftung.
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
@@ -199,4 +199,4 @@
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
-   limitations under the License.
+   limitations under the License.