chore: Remove ttlAfterNotRegistered value from settings

[jonathan-innis]

Fixes #

Description

Remove ttlAfterNotRegistered value from settings, making this value no longer configurable but set to a heuristic value of 15m, which is the time between when the Machine is created and when we expect the Node to register with the cluster

How was this change tested?

make presubmit

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[coveralls]

Pull Request Test Coverage Report for Build 4535367506

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• 23 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.02%) to 81.495%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/machine/garbagecollect.go	2	81.82%
pkg/operator/controller/typed.go	2	93.55%
pkg/controllers/deprovisioning/controller.go	3	82.49%
pkg/controllers/node/controller.go	7	73.53%
pkg/controllers/deprovisioning/events/events.go	9	85.25%

Totals
Change from base Build 4493525613:	-0.02%
Covered Lines:	6575
Relevant Lines:	8068

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💛 - Coveralls

[bwagner5]

LGTM, don't forget to update docs and helm chart

[jonathan-innis]

LGTM, don't forget to update docs and helm chart

This wasn't added to the main helm chart and the docs were never updated for this change ✅