[DOCS] Fix ML latency definition (elastic/x-pack-elasticsearch#2091)
[DOCS] Fix ML latency definition (elastic/x-pack-elasticsearch#2091)

Original commit: elastic/x-pack-elasticsearch@78c9cb387c689235b35d697d75c882493a8f9d70

nknize/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,GlenRSmith/elasticsearch,gfyoung/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,uschindler/elasticsearch,gfyoung/elasticsearch,coding0011/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,gfyoung/elasticsearch,GlenRSmith/elasticsearch,gfyoung/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,uschindler/elasticsearch,HonzaKral/elasticsearch,coding0011/elasticsearch