Temporarily pin uniffi-dart branch

Point payjoin-ffi at the merged chavic/fix-dart-error-object-naming
branch for testing. This lets the Dart generator fix be exercised on
this branch before a new uniffi-dart release tag is available.

Author: chavic

payjoin-ffi/Cargo.toml

@@ -34,7 +34,7 @@ thiserror = "2.0.14"
 tokio = { version = "1.47.1", features = ["full"], optional = true }
 uniffi = { version = "0.30.0", features = ["cli"] }
 uniffi-bindgen-cs = { git = "https://github.com/chavic/uniffi-bindgen-cs.git", rev = "878a3d269eacce64beadcd336ade0b7c8da09824", optional = true }
-uniffi-dart = { git = "https://github.com/Uniffi-Dart/uniffi-dart.git", tag = "v0.1.0+v0.30.0", optional = true }
+uniffi-dart = { git = "https://github.com/chavic/uniffi-dart.git", branch = "chavic/fix-dart-error-object-naming", optional = true }
 url = "2.5.4"
 
 # getrandom is ignored here because it's required by the wasm_js feature