Update dev xdr hash (#1400)

### What

The stellar-xdr dev dependency wasn't updated in the previous PR. This
PR updates it.

### Why

[TODO: Why this change is being made. Include any context required to
understand the why.]

### Known limitations

[TODO or N/A]

Author: jayz22

Cargo.lock

@@ -95,7 +95,7 @@ p256 = {version = "=0.13.2", default-features = false, features = ["alloc"]}
 [dev-dependencies.stellar-xdr]
 version = "=20.1.0"
 git = "https://github.com/stellar/rs-stellar-xdr"
-rev = "3a001b1fbb20e4cfa2cef2c0cc450564e8528057"
+rev = "a80c899c61e869fd00b7b475a4947ab6aaf9dcac"
 default-features = false
 features = ["arbitrary"]