Pending Transaction doesn't disappear out of Apple Wallet
To remove the duplicate transaction you need to refresh your Apple Wallet transactions by removing your Apple Card and re-adding it.
Go to Apple Wallet, select your Apple Card, click the 3 dots on the top right, scroll to the bottom, and click on Remove This Card.
You can then add your card back by clicking the + on the top right of the main Apple Wallet screen. Once it's added back, your transactions should be refreshed and the pending transaction should be gone.