Update .env

upgrade image tag

examples/mattermost/.env

@@ -36,7 +36,7 @@ MM_BLEVESETTINGS_INDEXDIR=/mattermost/bleve-indexes
 
 ## This will be 'mattermost-enterprise-edition' or 'mattermost-team-edition' based on the version of Mattermost you're installing.
 MATTERMOST_IMAGE=mattermost-enterprise-edition
-MATTERMOST_IMAGE_TAG=7.8
+MATTERMOST_IMAGE_TAG=release-9.3
 
 ## Make Mattermost container readonly. This interferes with the regeneration of root.html inside the container. Only use
 ## it if you know what you're doing.