Update an existing cost alert rule by ID. This example demonstrates:

• granularity: 3 (specific day in week) with dayInWeek: 5 (Saturday)
• changeType: "decrease" (detect cost decreases)
• alertLevel: "linked_account" (account-level monitoring)
• operator: "IS_NOT" (exclusion filter)
• costType: "net_amortized" (net amortized cost calculation)