Merge pull request 'Update Rust crate syn to v2' (#13) from renovate/syn-2.x into master

Reviewed-on: #13

src/reprc_proc_macro/Cargo.toml

@@ -9,5 +9,5 @@ proc-macro = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-syn = { version = "1.0.109", features = ["full", "fold"] }
+syn = { version = "2.0.4", features = ["full", "fold"] }
 quote = "1.0.26"