[7.4] [ML][Transforms] fix bwc serialization with 7.3 (#48021)#48052

Merged

benwtrent merged 1 commit intoelastic:7.4from benwtrent:backport/7.4/pr-48021

Oct 15, 2019

+33-3

Commits on Oct 15, 2019

[ML][Transforms] fix bwc serialization with 7.3 (elastic#48021 )
benwtrent
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