Wrong actor ID is used when creating a note linked to an episode
### Describe the bug
When you create a note that is linked to an episode, the wrong actor id is used (probably the podcast id instead of the actor id)
### Steps to reproduce
1. Empty database, install castopod from scratch
2. Before creating a podcast, run `ALTER TABLE cp_podcasts AUTO_INCREMENT=2;` on mysql
3. Create a podcast from Castopod admin panel (podcast id = 2, podcast actor id = 1)
4. Follow that podcast from a remote Mastodon server (follower actor id = 2)
5. Create an episode from Castopod admin panel
6. Create a note for that episode
### Expected behavior
Note should be created by the podcast actor.
### Actual behavior
Note is created by actor whose id is 2 instead on 1.
### Relevant logs and/or screenshots

### Context
- Castopod: alpha-49
- OS: any
- Browser: any
- Web server: any
### Possible fixes
Use the correct id. ;-)
issue