Remove redundant requireAdmin

We already hand out scopes based on the user's access control

src/routes/users.js

@@ -7,7 +7,6 @@ exports = module.exports = {
     create: create,
     remove: remove,
     verifyPassword: verifyPassword,
-    requireAdmin: requireAdmin,
     sendInvite: sendInvite,
     setGroups: setGroups
 };
@@ -146,17 +145,6 @@ function verifyPassword(req, res, next) {
     });
 }
 
-/*
-    Middleware which makes the route only accessable for the admin user.
-*/
-function requireAdmin(req, res, next) {
-    assert.strictEqual(typeof req.user, 'object');
-
-    if (!req.user.admin) return next(new HttpError(403, 'API call requires admin rights.'));
-
-    next();
-}
-
 function sendInvite(req, res, next) {
     assert.strictEqual(typeof req.params.userId, 'string');