Remove syn

This hasn’t been directly used since #64.

Signed-off-by: Anders Kaseorg <[email protected]>

Author: andersk

gc_derive/Cargo.toml

@@ -15,7 +15,6 @@ name = "gc_derive"
 proc-macro = true
 
 [dependencies]
-syn = "2.0"
 proc-macro2 = "1.0"
 quote = "1.0"
 synstructure = "0.13"