Merge branch 'update-mattermost-tag-7.3.0-bb.0' into 'master'

Mattermost update to 7.3.0

Closes platform-one/big-bang/apps/collaboration-tools/mattermost#56

See merge request platform-one/big-bang/bigbang!2132

chart/values.yaml

@@ -1231,7 +1231,7 @@ addons:
     git:
       repo: https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost.git
       path: "./chart"
-      tag: "7.2.0-bb.1"
+      tag: "7.3.0-bb.0"
 
     # -- Flux reconciliation overrides specifically for the Mattermost Package
     flux: {}