Update to thiserror 2 (#215)

[This is pretty widespread now](https://lib.rs/crates/thiserror/rev)
(and will be more so by the next Proj release).

Author: TomFryersMidsummer

Cargo.toml

@@ -18,7 +18,7 @@ proj-sys = { version = "0.25.0", path = "proj-sys" }
 geo-types = { version = "0.7.10", optional = true }
 libc = "0.2.119"
 num-traits = "0.2.14"
-thiserror = "1.0.30"
+thiserror = "2.0.0"
 ureq = { version = "2.0.0", optional = true }
 
 [workspace]