fix(plugins): remove invalid mcp_servers key from plugin.json files

The mcp_servers key is not a valid key in the Claude plugin manifest
schema. MCP servers are configured in the root .mcp.json file instead.

Affected plugins:
- cmdb-assistant
- contract-validator
- data-platform
- pr-review
- projman
- viz-platform

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/viz-platform/.claude-plugin/plugin.json

@@ -19,6 +19,5 @@
     "visualization",
     "dmc"
   ],
-  "mcp_servers": ["viz-platform"],
   "commands": ["./commands/"]
 }