Remove outdated import in r-a proc macro server.

Author: m-ou-se

src/tools/rust-analyzer/crates/proc-macro-srv/src/server.rs

@@ -8,10 +8,7 @@
 //!
 //! FIXME: No span and source file information is implemented yet
 
-use proc_macro::{
-    bridge::{self, server},
-    LineColumn,
-};
+use proc_macro::bridge::{self, server};
 
 mod token_stream;
 pub use token_stream::TokenStream;