[8.0](backport #28671) Remove auto option from setup.ilm.enabled and set the default value to true

[mergify]

This is an automatic backport of pull request #28671 done by Mergify.

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[elasticmachine]

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• Start Time: 2021-11-15T09:41:15.123+0000

• Duration: 108 min 1 sec

• Commit: 75849d3

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Test	Results
Failed	0
Passed	54107
Skipped	5346
Total	59453

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