[DOCS] Update 7.0 migration docs with Elastic Maps Service changes (#…

…31321)

* Update 7.0 migration docs with Elastic Maps Service changes

docs/migration/migrate_7_0.asciidoc

@@ -8,6 +8,7 @@ This section discusses the changes that you need to be aware of when migrating
 your application to Kibana 7.0.
 
 * <<breaking_70_setting_changes>>
+* <<breaking_70_ems_changes>>
 
 See also <<release-highlights>> and <<release-notes>>.
 
@@ -407,3 +408,21 @@ a table; it only restricts the number of split tables to one.
 migrated to contain only one split table, converting any existing split tables beyond the first to split rows. No action
 should be required as a result of this change, but be aware that users with saved data table visualizations that contain
 multiple split tables will now see those tables rendered differently.
+
+[float]
+[[breaking_70_ems_changes]]
+=== Elastic Maps Service changes
+
+[float]
+==== Removed overseas territories from France Departments vector layer
+
+*Details:* Overseas territories in the France Departments vector layer have been removed. These territories have no ISO 3166-2 or INSEE codes to join to Elasticsearch data.
+
+*Impact:* Region Map, Vega, and Maps plugin visualizations using the France Departments layer will not show overseas territories. 
+
+[float]
+==== USA Zip Codes vector layer updated with latest US Census data
+
+*Details:* The USA Zip Codes layer has been updated based on the https://www.census.gov/geo/reference/zctas.html[2018 Zip Code Tabulation Areas (ZCTAs)] distributed by the US Census Bureau. ZCTA boundaries have been generalized from the source data for visualization and locations are approximate.
+
+*Impact:* Region Map, Vega, and Maps plugin visualizations using the USA Zip Codes layer will appear differently. ZCTA boundaries have changed dramatically in some areas. Also, some zip codes have been deprecated and new ones have been added.