Removing redundant check for transaction in progress in check_safe_enum_use

Hi,
I was looking at :
Relax transactional restrictions on ALTER TYPE ... ADD VALUE (redux).

In check_safe_enum_use():

+ if (!TransactionIdIsInProgress(xmin) &&
+ TransactionIdDidCommit(xmin))
+ return;

Since the condition would be true only when TransactionIdDidCommit()
returns true, I think the call to TransactionIdIsInProgress is not needed.
If transaction for xmin is committed, the transaction cannot be in progress
at the same time.

Please see the simple patch for removing the redundant check.

Thanks