Update graphs in Protocols section

- Open and Transact Phase - Ledger channel: Unclear descriptions of "if user didn not respond within expected time"

- Settling Protocol - Ledger channel: The arrow "withdraw from channel" of Bob pointing in the wrong direction

Start in the Protocols section and locate the graph sources for the Open and Transact Phase and Settling Protocol Ledger-channel diagrams. Clarify the description of the no-response condition and correct Bob’s “withdraw from channel” arrow direction. Done means both graphs accurately reflect the intended protocol flow.

Written by the indexing model from the issue text.