fix(chart): correct ha-mcp image tag from v6.7.1 to 6.7.1

The ghcr.io/homeassistant-ai/ha-mcp registry publishes tags without
the 'v' prefix, causing ErrImagePull when the sidecar is enabled.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

README.md

@@ -221,7 +221,7 @@ mcpSidecars:
     enabled: true
     image:
       repository: ghcr.io/homeassistant-ai/ha-mcp
-      tag: v6.7.1  # Override the pinned version if needed
+      tag: 6.7.1  # Override the pinned version if needed
     port: 8087
     resources:
       requests: