Update json-iterator vendor to v1.1.5

We already have it vendored for a Kube package we import, but we
want a more recent version with additional bugfixes over the 1.0
release we originally had.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

vendor/github.com/modern-go/concurrent/executor.go

@@ -0,0 +1,14 @@
+package concurrent
+
+import "context"
+
+// Executor replace go keyword to start a new goroutine
+// the goroutine should cancel itself if the context passed in has been cancelled
+// the goroutine started by the executor, is owned by the executor
+// we can cancel all executors owned by the executor just by stop the executor itself
+// however Executor interface does not Stop method, the one starting and owning executor
+// should use the concrete type of executor, instead of this interface.
+type Executor interface {
+	// Go starts a new goroutine controlled by the context
+	Go(handler func(ctx context.Context))
+}