Tenor API deprecated - let Gifbox use other services e.g. Giphy

[arcartis]

Replace Tenor for Giphy or other GIF service

Since the gifbox image from docker has the Tenor service hard coded and Tenor is no longer accepting new API clients (see the docs here, the gifbox is no longer working for new setups due to the missing API key.

I would suggest to leave it open for self hosters to pick a service of choice, or perhaps pick giphy as a replacement for now.

From the Google support docs:

[Dadadah]

New feature requests must be vetted by the Stoat org. Please discuss feature requests in the official channels.