Revert "Added precaution to avoid creating multiple Complimentary plans"

This reverts commit 5f0d2168f3.

After discussing the best approach to multipe currency problem would be
to allow creating multiple "Complimentary" plans. All security related
checks should stay strictly based on name and would not cause issues.

ghost/members-api/lib/stripe/index.js

@@ -36,11 +36,6 @@ module.exports = class StripePaymentProcessor {
 
             this._plans = [];
             for (const planSpec of config.plans) {
-                // NOTE: we have only one "Complimentary" plan throughout the system
-                if (planSpec.name === 'Complimentary' && planSpec.currency !== 'usd') {
-                    return;
-                }
-
                 const plan = await api.plans.ensure(this._stripe, planSpec, this._product);
                 this._plans.push(plan);
             }