Removing Discover from credit card dropdown

I am using version 2.20 and I would like to remove Discover card from the payment options in Payments.AuthorizeNet.

I can't find the code anywhere. Can you help me out?

In 2.3, it's hardcoded into PaymentAuthorizeNetController.cs in the PaymentInfo action.  You'll need to remove it there and recompile.

I am using nopCommerce 2.20 not 2.3.

I know, I'm just saying that's how it is in 2.3 because I don't have 2.2 to look at.  Take a look at the code and see if it's the same.

What is the path to that page?

/Plugins/Nop.Plugin.Payments.AuthorizeNet/Controllers/PaymentAuthorizeNetController.cs

I don't have the folder /Plugins/Nop.Plugin.Payments.AuthorizeNet.

I have /Plugins/Payments.AuthorizeNet but I don't have any folders inside of that.

Did you only download the NoSource option of nopCommerce?  You're going to need the source code and the ability to compile it to make this change.  It's not just a config file.