snapd: Update confinement warning with a date

[davidjharder]

Summary

• Add a sentence to the warning which runs for every snap, telling users that snaps will stop working soon.
• Part of Snap/Apparmor deprecation #325
• See also snap.md: Update warning with deprecation date help-center-docs#589

Sync Message:

The warning that pops up whenever you run a snap has been changed to include the sentence "Snaps will stop working in early January 2025." This is part of a process we started back in July to remove snap support from Solus; we wrote about our reasons for this in a blog post. The Help Center has a page with more details about the warning and what you can do if you have snaps installed. Most users will not have snaps installed, as Solus has usually recommended that third-party apps be installed from the Third Party section of the Solus Software Center or as Flatpaks.

Test Plan

• Run a CLI snap, see changed warning
• Graphical warning untested

Checklist

• Package was built and tested against unstable
• This change could gainfully be listed in the weekly sync notes once merged

[TraceyC77]

Tested this on my laptop - pass

• Built and installed the eopkg from this PR
• Started a snap from command line
• Read output

Result: I saw the updated text, output is formatted correctly
This is the output

❯ git st
On branch snapd-warning
Your branch is up to date with 'origin/snapd-warning'.

❯ /snap/bin/spotify
WARNING: snap is running with partial confinement. Snaps will stop working in early January 2025. See https://help.getsol.us/docs/user/software/third-party/snap for details

Also installed termius and tested with that, also good.

Running any snap from the app menu produces no warning whatsoever. That's unrelated to this change, I'll file a separate issue for that.

[TraceyC77]

Looks good, and testing passed.