chore: fix renovate config to only allow semver on mattermost image (#51

)

## Description
fix renovate config to only allow semver on mattermost image

## Related Issue

Fixes #

[50](#50)

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [x] Other (security config, docs update, etc)

## Checklist before merging

- [ ] Test, docs, adr added or updated as needed
- [ ] [Contributor Guide
Steps](https://github.com/defenseunicorns/uds-package-mattermost/blob/main/CONTRIBUTING.md#developer-workflow)
followed

renovate.json

@@ -23,6 +23,14 @@
       "commitMessageTopic": "package-deps",
       "matchDatasources": ["docker", "helm", "git-tags"]
     },
+    {
+      "groupName": "Mattermost Package Dependencies",
+      "labels": ["package-deps"],
+      "commitMessageTopic": "package-deps",
+      "matchDatasources": ["docker"],
+      "matchPackagePatterns": ["mattermost/mattermost-enterprise-edition"],
+      "allowedVersions": "/^\\d+\\.\\d+\\.\\d+$/"
+    },
     {
       "groupName": "Mattermost Package Dependencies",
       "labels": ["package-deps"],