zjsunit: Simplify typeRoots path (it’s relative to tsconfig.json).

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

frontend_tests/zjsunit/index.js

@@ -1,7 +1,7 @@
 require('ts-node').register({
     project: 'static/js/tsconfig.json',
     compilerOptions: {
-        typeRoots: ["node_modules/@types", "../../static/js/js_typings"],
+        typeRoots: ["node_modules/@types", "./js_typings"],
         // We don't have webpack to handle es6 modules here so directly
         // transpile to CommonJS format.
         module: "commonjs",