Ensure to close StreamFrame channel (#12248)

.changelog/12248.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+api: `AllocFS.Logs` now explicitly closes frames channel after being canceled
+```

api/fs.go

@@ -257,6 +257,7 @@ func (a *AllocFS) Logs(alloc *Allocation, follow bool, task, logType, origin str
 			// Check if we have been cancelled
 			select {
 			case <-cancel:
+				close(frames)
 				return
 			default:
 			}