Update `backend` Kinvolk references to Flatcar

[tylerauerbeck]

Update backend Kinvolk references to Nebraska

There are still many references to Kinvolk throughout the repository. It makes sense to get these updated to Flatcar now that everything has been migrated to the flatcar org. This PR updates all of the references in the root of the repo (README, helm chart) and those in the backend module to use Flatcar to begin this transition.

Begins to address #1090

How to use

Functionally nothing changes, the application can be used as it normally is

Testing done

make backend

• [X] Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• [X] Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

[tylerauerbeck]

@tormath1 Alright, this should look a bit better now.

[tylerauerbeck]

@tormath1 Any idea if there's a better contact email for spec.yaml than [email protected] ?

[ervcz]

@tormath1 Any idea if there's a better contact email for spec.yaml than [email protected] ?

It would be safe to use [email protected]. This email address is also mentioned in the readme.

[tylerauerbeck]

@ervcz @tormath1 Fixed lints and updated the email in the api spec. Let me know if we need anything else here.

[tylerauerbeck]

Alright, 🤞🏻 this should be in the right shape now.