rust: Update thiserror to match fuchsia

Test: cargo check
Change-Id: If9a6be8ffe573c718e82080e9c29bea36a6a6964
Reviewed-on: https://bluetooth-review.googlesource.com/c/bluetooth/+/3700

rust/Cargo.toml

diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index be959b5..f0a9142 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -31,5 +31,5 @@
 parking_lot = "0.12.5"
 pin-project = "1.1"
 pretty_assertions = "1.4.1"
-thiserror = "2.0.18"
+thiserror = "2.0.20"
 uuid = { version = "1.23.3", features = ["serde", "v4"] }