[Bug]: Exclude themes in PATCH requests for eula and privacy policy fields

[ioanarusiczki]

What happened?

From #14927 (comment)

What did you expect to happen?

There should be an error message when attempting to send eula or privacy policy for static themes.

Is there an existing issue for this?

• I have searched the existing issues

┆Issue is synchronized with this Jira Task

[ioanarusiczki]

I tried with
https://addons-dev.allizom.org/api/v5/addons/addon/631762/eula_policy/
or https://addons-dev.allizom.org/api/v5/addons/addon/632181/eula_policy/ and I got a 200 response.
https://addons-dev.allizom.org/en-US/firefox/addon/blue-overdose-theme_blue/

Could there be a deploy issue?

[ioanarusiczki]

I can no longer send a patch request for a theme id/guid/slug.
Addons, dicts or lang packs can have eula and/or privacy policy.