pkg/assets/internal: remove critical pod annotations

[squat]

This PR mirrors the work done in coreos/tectonic-installer#1702 to remove the critical pod annotations for control-plane components.
Question: do we also want to remove these annotations from kube-dns and calico?

cc @diegs cc @aaronlevy

[diegs]

I think we should remove them from all--they're only relevant for the rescheduler.

[diegs]

LGTM assuming this is all of them.

[dghubble]

I still spot a few references on calico, calico (canal), and kube-dns. cc @squat

pkg/asset/internal/templates.go:        scheduler.alpha.kubernetes.io/critical-pod: ''
pkg/asset/internal/templates.go:        scheduler.alpha.kubernetes.io/critical-pod: ''
pkg/asset/internal/templates.go:        scheduler.alpha.kubernetes.io/critical-pod: ''

[dghubble]

Friendly ping @squat or should we modify this in a separate PR?

[squat]

This fell off my radar. Let me push a new commit

[dghubble]

Superceded by #777