Fix needed: Typo in Figure A-7

[shaurya947]

Describe the error
Figure A-7 uses incorrect characters when referencing Bob's TxID within Chan's TX. The last 16 characters of Bob's TxID are 281c891ac13f1005. However, inside Chan's TX, the last 16 characters are written as c9c2891ac13f1005.

To Fix
Within Chan's TX, use the correct last 16 characters of Bob's TxID as 281c891ac13f1005.