[Transform] remove transform remote connect

[hendrikmuhs]

The late addition: #53924
introduces the ability to query for nodes that can connect to remote clusters.

This makes TRANSFORM_REMOTE_ENABLED_NODE_ATTR introduced in #52712 superflous. Because #52712 targets 7.7, which means unreleased, it makes sense to remove the setting for 7.7 to circumvent a deprecation cycle.

This should go in, into 7.7 despite FF, the change is low risk.

/CC @jasontedor @droberts195

(There seems no appropriate label, using >non-issue for now as its unreleased und should not be picked up for release notes.)

[elasticmachine]

Pinging @elastic/ml-core (:ml/Transform)

[jasontedor]

This sounds good to me!