deploy: update prod to v1.7.9 (#1282)

Promotes
[v1.7.9](https://github.com/modelcontextprotocol/registry/releases/tag/v1.7.9)
to production. Includes the OCI validator fail-closed fix from #1281.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: rdimitrov

deploy/Pulumi.gcpProd.yaml

@@ -1,7 +1,7 @@
 config:
   mcp-registry:environment: prod
   mcp-registry:provider: gcp
-  mcp-registry:imageTag: 1.7.8  # Set specific image tag for production (change this to deploy different versions)
+  mcp-registry:imageTag: 1.7.9  # Set specific image tag for production (change this to deploy different versions)
   gcp:project: mcp-registry-prod
   mcp-registry:githubClientId: Iv23liUydBbI7Z2Q9bOZ
   mcp-registry:githubClientSecret: