Fix comment with path to symbols! macro

Author: mgacek8

compiler/rustc_span/src/symbol.rs

@@ -18,7 +18,7 @@ use crate::{Edition, Span, DUMMY_SP, SESSION_GLOBALS};
 #[cfg(test)]
 mod tests;
 
-// The proc macro code for this is in `src/librustc_macros/src/symbols.rs`.
+// The proc macro code for this is in `compiler/rustc_macros/src/symbols.rs`.
 symbols! {
     // After modifying this list adjust `is_special`, `is_used_keyword`/`is_unused_keyword`,
     // this should be rarely necessary though if the keywords are kept in alphabetic order.