fix: standardize billing-cost-management server id convention (#1549)

Update server ID and source_path from underscore to hyphen format to fix
broken links and ensure consistency with other MCP server naming patterns.

- Change ID: billing_cost_management_mcp_server → billing-cost-management-mcp-server
- Update path: src/billing_cost_management_mcp_server/ → src/billing-cost-management-mcp-server/

This resolves broken documentation links caused by inconsistent naming.

Author: knziiy

docusaurus/static/assets/server-cards.json

@@ -976,9 +976,9 @@
       "category": "Cost & Operations",
       "description": "AWS Billing and Cost Management",
       "icon": "\ud83d\udcb0",
-      "id": "billing_cost_management_mcp_server",
+      "id": "billing-cost-management-mcp-server",
       "name": "AWS Billing and Cost Management MCP Server",
-      "source_path": "src/billing_cost_management_mcp_server/",
+      "source_path": "src/billing-cost-management-mcp-server/",
       "subcategory": "Cost Management",
       "tags": [
         "billing",