Fix order of API and mark language as readonly (#15216)

src/api.d.ts

@@ -210,19 +210,19 @@ export type KernelStatus =
  * Represents a Jupyter Kernel.
  */
 export interface Kernel {
-    /**
-     * The current status of the kernel.
-     */
-    readonly status: KernelStatus;
     /**
      * An event emitted when the kernel status changes.
      */
     onDidChangeStatus: Event<KernelStatus>;
+    /**
+     * The current status of the kernel.
+     */
+    readonly status: KernelStatus;
     /**
      * Language of the kernel.
      * E.g. python, r, julia, etc.
      */
-    language: string;
+    readonly language: string;
     /**
      * Executes code in the kernel without affecting the execution count & execution history.
      *