fix(a11y): remove alt text for decorative image

Because:

* Adjacent text explains the meaning, making the additional text unnecessary.

This commit:

* Removes alt tag copy.

Closes FXA-3047

packages/fxa-payments-server/src/components/PaymentConfirmation/index.tsx

@@ -90,11 +90,7 @@ export const PaymentConfirmation = ({
         <header className="flex flex-col justify-center items-center row-divider-grey-200 text-center pb-8 mt-5 desktop:mt-2">
           {accountExists ? (
             <>
-              <img
-                className="max-h-12"
-                src={circledCheckbox}
-                alt="circled checkbox"
-              />
+              <img className="max-h-12" src={circledCheckbox} alt="" />
               <Localized id="payment-confirmation-thanks-heading">
                 <h2 className={h2classes}>Thank you!</h2>
               </Localized>