upgrade to syn 2 in c2rust-ast-builder

Author: bungcip

c2rust-ast-builder/Cargo.toml

@@ -13,4 +13,4 @@ categories.workspace = true
 
 [dependencies]
 proc-macro2 = { version = "1.0", features = ["span-locations"]}
-syn = { version = "1.0", features = ["full", "extra-traits", "printing", "clone-impls"]}
+syn = { version = "2.0", features = ["full", "extra-traits", "printing", "clone-impls"]}