headlamp-plugin/plugin-management.test: Add #! to top of file

So test can be more easily executed.

Signed-off-by: René Dudfield <renedudfield@microsoft.com>

plugins/headlamp-plugin/headlamp-plugin-management.test.js

@@ -1,3 +1,4 @@
+#!/bin/env node
 const { execSync } = require('child_process');
 const assert = require('assert');
 const fs = require('fs');