Update test jwt payload to be correct

Becuase of additional validation that was added https://github.com/Shopify/shopify-api-ruby/pull/1369/files#diff-06572a96a58dc510037d5efa622f9bec8519bc1beab13c9f251e97e657a9d4ed

This test began to fail

Author: lizkenyon

test/shopify_app/controller_concerns/with_shopify_id_token_test.rb

@@ -17,7 +17,7 @@ def setup
     @id_token = "this-is-the-shopify-id-token"
     @auth_header = "Bearer #{@id_token}"
     @jwt_payload = {
-      iss: "iss",
+      iss: "https://test-shop.myshopify.com/admin",
       dest: "https://test-shop.myshopify.com",
       aud: ShopifyAPI::Context.api_key,
       sub: "1",