CI: remove "experimental" checks, as they may be redundant

[thaJeztah]

Description

While working on #5139, I noticed that CI was green even if we didn't enable experimental on the daemon.

I was curious how the experimental and non-experimental e2e tests differed, and after a cursory glance, it may be only for a single test;

cli/e2e/image/build_test.go

Line 128 in 591bd17

environment.SkipIfNotExperimentalDaemon(t)

If that's correct, then it would mean we run all e2e tests twice, but only for a single test; we can cut the number of checks in half if we don't do so;

• Always enable experimental on the daemon (we already do so!)
• Run the tests and let the "experimental" one be skipped
• Rejoice!