fix(usage): reword the plan hint when we have no billing period (#8430)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: talissoncosta

frontend/web/components/pages/usage/__tests__/utils.test.ts

@@ -106,8 +106,8 @@ describe('UsageDashboard utils', () => {
 
       expect(basis).toEqual({ reason: 'free', window: 'rolling' })
       expect(allowanceWindow(basis)).toBeUndefined()
-      expect(planSectionCopy(basis, 50000).hint).not.toContain(
-        'no billing period',
+      expect(planSectionCopy(basis, 50000).hint).toBe(
+        'Usage against your plan limit over the last 30 days.',
       )
     })
 
@@ -119,7 +119,7 @@ describe('UsageDashboard utils', () => {
 
       expect(basis).toEqual({ reason: 'no-period', window: 'rolling' })
       expect(planSectionCopy(basis, 50000).hint).toContain(
-        'has no billing period',
+        'unable to show exact billing periods',
       )
     })
   })

frontend/web/components/pages/usage/utils.ts

@@ -46,7 +46,7 @@ export const planSectionCopy = (
     return {
       hint: `Usage against your plan limit over ${allowanceWindowLabel(
         basis,
-      )}. This organisation has no billing period.`,
+      )}. We are unable to show exact billing periods for your subscription plan.`,
       title: 'Your plan',
     }
   }