Remove unneeded syn feature

Author: yaahc

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "displaydoc"
-version = "0.1.2"
+version = "0.1.3"
 authors = ["Jane Lusby <jlusby@yaah.dev>"]
 edition = "2018"
 license = "MIT"
@@ -19,6 +19,6 @@ proc-macro = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-syn = { version = "1.0", features = ["extra-traits"] }
+syn = "1.0"
 quote = "1.0"
 proc-macro2 = "1.0"