dependencies: Upgrade to webpack-bundle-tracker 1.0.0-alpha.1.

This also seems unmaintained, but is, at least, released.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

static/js/types/webpack4-bundle-tracker/index.d.ts

@@ -1,16 +0,0 @@
-import {Plugin} from "webpack";
-
-declare namespace BundleTracker {
-    interface Options {
-        path?: string;
-        filename?: string;
-        publicPath?: string;
-        logTime?: boolean;
-    }
-}
-
-declare class BundleTracker extends Plugin {
-    constructor(options?: BundleTracker.Options);
-}
-
-export = BundleTracker;