Merge pull request #180 from humanmade/backport-179-to-v5-branch

[Backport v5-branch] Update v5 upgrade guide regarding reindexing

other-docs/guides/upgrading/v5.md

@@ -87,7 +87,9 @@ Altis 5 now includes the ability to specify custom user dictionaries used during
 
 Other changes included in the update to ElasticPress 3.4 also include the ability for users to adjust individual search queries, allowing results to be manually tuned or overridden, as well as better WooCommerce integration out of the box.
 
-Reindexing is not required for these changes. When user dictionaries are changed, any relevant content will be automatically reindexed.
+Reindexing is not required for changes to fuzzy matching but _is_ required when user dictionaries are changed, unless using Elasticsearch version 7.8 or higher.
+
+Elasticsearch 7.8+ support is currently experimental, please contact support if you wish to try upgrading.
 
 
 ### Suggestions when searching