Include Note that All MOJOs are Thread Safe in the User Guide

[exalate-issue-sync]

In the [productionizing section|http://docs.h2o.ai/h2o/latest-stable/h2o-docs/productionizing.html] let's add a note that states which algorithm's POJO/MOJOs are thread-safe.

All algorithm's should be thread-safe except for Deep Learning. We can point to the following JIRA tickets to track when DL becomes thread-safe:
https://0xdata.atlassian.net/browse/PUBDEV-2664
https://0xdata.atlassian.net/projects/PUBDEV/issues/PUBDEV-6680

[exalate-issue-sync]

Angela Bartz commented: Pull request #3974 submitted to rel-yau.

[exalate-issue-sync]

Angela Bartz commented: Pull requests merged into rel-yu and master.

[h2o-ops]

JIRA Issue Migration Info

Jira Issue: PUBDEV-6964
Assignee: Angela Bartz
Reporter: Lauren DiPerna
State: Resolved
Fix Version: 3.28.0.4
Attachments: N/A
Development PRs: Available

Linked PRs from JIRA

#3974
#4338