Removed Buttons colors for V2

[stechiu]

Reason for changes

We will remove the deprecated colors in V2

Summary of changes

• Removed .black, .silver, .blue, and .darkBlue as per QL button redesign requirements

Checklist

• [x] Added a changelog entry

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @stechiu

[warmkesselj]

@stechiu does this enum embedded in PayPalButton need updating?

    /// Available colors for PayPalButton.
    public enum Color: String {
        case gold
        case white
        case black
        case silver
        case blue

        var color: PaymentButtonColor {
            PaymentButtonColor(rawValue: rawValue) ?? .gold
        }
    }

[stechiu]

@stechiu does this enum embedded in PayPalButton need updating?

    /// Available colors for PayPalButton.
    public enum Color: String {
        case gold
        case white
        case black
        case silver
        case blue

        var color: PaymentButtonColor {
            PaymentButtonColor(rawValue: rawValue) ?? .gold
        }
    }

Missed this one, thanks!

[jaxdesmarais]

It looks like we will also need to clean up the demo app with these changes. See: https://github.com/paypal/paypal-ios/blob/157712a6b10849ac105acdac0e24be995211657a/Demo/Demo/Extensions/PaymentButtonEnums%2BExtension.swift#L14