Since these docs were originally written there have been a couple
of changes:
1. We now support aarch64 as well as x86_64, so the SSE4.2 guidance
needed clarification.
2. ML is more deeply embedded into Elasticsearch functionality
across nodes that are not ML nodes. For example, ingest pipelines
now routinely use ML, and, in the near future, index mappings
will too in the form of semantic text. Although we cannot mandate
that xpack.ml.enabled is set uniformly across the cluster, as
that would be a breaking change, we should say ever more strongly
that ML must be enabled on all nodes if all ML functionality is to
work correctly. The primary reason for wanting to disable ML is
hardware incompatibility, and if ML is disabled for that reason
then it should not be used at all.
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