remove unused import

Author: Empty2k12

influxdb_derive/src/writeable.rs

@@ -1,7 +1,6 @@
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 use std::convert::TryFrom;
-use syn::spanned::Spanned;
 use syn::{
     parse::{Parse, ParseStream},
     punctuated::Punctuated,