fix(note): fix type for owner param

To make the create method easier to use in conjunction
with the authentication framework, this commit changes the type of
the `owner` parameter from `User | undefined` to `User | null`.

Signed-off-by: David Mehren <git@herrmehren.de>

test/public-api/media.e2e-spec.ts

@@ -38,6 +38,7 @@ describe('Media', () => {
     user = await testSetup.userService.createUser('hardcoded', 'Testy');
     testNote = await testSetup.notesService.createNote(
       'test content',
+      null,
       'test_upload_media',
     );
   });