[ML][DOCS] Fix bucket_span type in results resources (elastic/x-pack-elasticsearch#2714)
[ML][DOCS] Fix bucket_span type in results resources (elastic/x-pack-elasticsearch#2714)

Original commit: elastic/x-pack-elasticsearch@7de7ab6160ea70fd705a05349e7122a4bc820562

vroyer/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra