Merge branch 'update-mattermost-tag-9.7.3-bb.0' into 'master'

mattermost update to 9.7.3-bb.0

Closes big-bang/product/packages/mattermost#116

See merge request !4268

chart/values.yaml

@@ -1643,11 +1643,11 @@ addons:
     git:
       repo: https://repo1.dso.mil/big-bang/product/packages/mattermost.git
       path: "./chart"
-      tag: "9.7.2-bb.0"
+      tag: "9.7.3-bb.0"
     helmRepo:
       repoName: "registry1"
       chartName: "mattermost"
-      tag: "9.7.2-bb.0"
+      tag: "9.7.3-bb.0"
 
     # -- Flux reconciliation overrides specifically for the Mattermost Package
     flux: {}