Update syn crate from 1.0.109 to 2.0.101 (#31301)

Nearly all generated by Zed Agent + Claude Opus 4. I just wrote the test
`Args` struct and pointed it at the [2.0 release
notes](https://github.com/dtolnay/syn/releases/tag/2.0.0).

Release Notes:

- N/A

Cargo.toml

@@ -550,7 +550,7 @@ streaming-iterator = "0.1"
 strsim = "0.11"
 strum = { version = "0.27.0", features = ["derive"] }
 subtle = "2.5.0"
-syn = { version = "1.0.72", features = ["full", "extra-traits"] }
+syn = { version = "2.0.101", features = ["full", "extra-traits"] }
 sys-locale = "0.3.1"
 sysinfo = "0.31.0"
 take-until = "0.2.0"