Remove grade devel from Certbot snap. (#8128)
Remove grade devel from Certbot snap. (#8128)

If you go to a URL like https://snapcraft.io/certbot/releases and try to move the Certbot snap into the candidate or stable channels, you cannot do so. There is a tooltip which says that revisions with the grade devel cannot be promoted to candidate or stable channels.

The documentation for `grade` can be found at https://snapcraft.io/docs/snapcraft-yaml-reference where it says the value is optional and

> Defines the quality grade of the snap.
Type: enum
Can be either devel (i.e. a development version of the snap, so not to be published to the stable or candidate channels) or stable (i.e. a stable release or release candidate, which can be released to all channels)
Example: [stable or devel]

I'm working on a proposal for our next steps for snaps which involves moving the Certbot snap to the stable channel. I of course won't make those changes without giving others a chance to share their opinion, but I'd like to avoid the situation where we're technically unable to move the Certbot 1.6.0 snap to the stable channel despite wanting to do so.

I started to make the same changes to the DNS plugins, but I personally think it's too soon to propose stable versions of those yet and `grade` is a simple way to ensure we don't accidentally promote something there.

You can see the snap being built and run successfully with this change at https://dev.azure.com/certbot/certbot/_build/results?buildId=2246&view=results.
stweil/letsencrypt,letsencrypt/letsencrypt,lmcro/letsencrypt,stweil/letsencrypt,lmcro/letsencrypt,letsencrypt/letsencrypt