[DOCS] Added ML sample data URLs (elastic/x-pack-elasticsearch#1256)
[DOCS] Added ML sample data URLs (elastic/x-pack-elasticsearch#1256)

Original commit: elastic/x-pack-elasticsearch@528a32f26f7f74de8e63aab3c2a6667c5c30e372

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