docs(asset-leasing): remove ASCII-art lifecycle diagram

ASCII art renders inconsistently across viewers (different fonts,
different terminal widths) and looks bad even when it works. Kept
the prose paragraph that follows it explaining the Closed/Liquidated
states aren't directly observable onchain — that's the useful bit.

State transitions are already covered narratively in section 3
(per-instruction walkthrough) and section 4 (full-lifecycle worked
examples). A diagram on top is redundant.

Author: Edward (OpenClaw)

defi/asset-leasing/anchor/README.md

@@ -252,28 +252,6 @@ pub struct Lease {
 }
 ```
 
-### Lifecycle diagram
-
-```
-                  create_lease
-               +---------------+
- (no lease) -> |    Listed     |
-               +---------------+
-                 |          |
-      take_lease |          | close_expired (holder cancels)
-                 v          v
-               +---------------+       +--------+
-               |    Active     | ----> | Closed |
-               +---------------+       +--------+
-                 |    |       |
-     return_lease|    |       | close_expired (after end_timestamp)
-                 |    | liquidate
-                 v    v       v
-             +--------+ +-----------+
-             | Closed | | Liquidated|
-             +--------+ +-----------+
-```
-
 The `Closed` and `Liquidated` states are not directly observable
 onchain: all three of `return_lease`, `liquidate` and `close_expired`
 close the `Lease` account in the same transaction (`close = holder`),