test,loader: remove skip from loader test

Removing the skip message from test since `data:text/javascript,`
is being used to bypass the required argument validation of the
--experimental-loader <required> flag.

test/es-module/test-esm-loader-programmatically.mjs

@@ -8,11 +8,11 @@ import { spawnPromisified } from '../common/index.mjs';
 // programmatically.
 
 describe('ESM: register loader programmatically', { concurrency: true }, () => {
-  it('should be able to register programmatically loader', {
-    skip: 'Skipping for now because --experimental-loader option is required to use the CustomModuleLoader'
-  }, async () => {
+  it('should be able to register programmatically loader', async () => {
     const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
       '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,',
       fixtures.path('/es-module-loaders/register-loader-entrypoint.mjs'),
     ]);