Always include Promise polyfill for legacy browsers

It is now used by our general code and not just by the conversion
routines, so we need to make sure it is always included for the
old browsers.

kasmweb/utils/use_require_helpers.js

@@ -31,7 +31,6 @@ module.exports = {
                     return [ require_path ];
                 });
         },
-        noCopyOverride: () => {},
     },
     'commonjs': {
         optionsOverride: (opts) => {
@@ -45,7 +44,6 @@ module.exports = {
                 .then(buf => writeFile(out_path, buf))
                 .then(() => []);
         },
-        noCopyOverride: () => {},
         removeModules: true,
     },
     'systemjs': {
@@ -55,17 +53,11 @@ module.exports = {
             return writeFile(out_path, `SystemJS.import("${ui_path}");`)
                 .then(() => {
                     console.log(`Please place SystemJS in ${path.join(script_base_path, 'system-production.js')}`);
-                // FIXME: Should probably be in the legacy directory
-                    const promise_path = path.relative(base_out_path,
-                                                       path.join(base_out_path, 'vendor', 'promise.js'));
                     const systemjs_path = path.relative(base_out_path,
                                                         path.join(script_base_path, 'system-production.js'));
-                    return [ promise_path, systemjs_path ];
+                    return [ systemjs_path ];
                 });
         },
-        noCopyOverride: (paths, no_copy_files) => {
-            no_copy_files.delete(path.join(paths.vendor, 'promise.js'));
-        },
     },
     'umd': {
         optionsOverride: (opts) => {