[Docs] - minor typo in docs/en/stack/ml/nlp/ml-nlp-elser.asciidoc

[jamie-wilson88]

Minor typo in:
docs/en/stack/ml/nlp/ml-nlp-elser.asciidoc
https://www.elastic.co/guide/en/machine-learning/current/ml-nlp-elser.html

"Using the traned models API in Dev Console"
Should be:
"Using the trained models API in Dev Console"

[kosabogi]

Related PR: #2871