tidy: Remove edition filter exceptions.

These exceptions are no longer necessary.

src/tools/tidy/src/edition.rs

@@ -2,20 +2,6 @@
 
 use std::path::Path;
 
-fn filter_dirs(path: &Path) -> bool {
-    // FIXME: just use super::filter_dirs after the submodules are updated.
-    if super::filter_dirs(path) {
-        return true;
-    }
-    let skip = [
-        "src/doc/book/second-edition",
-        "src/doc/book/2018-edition",
-        "src/doc/book/ci/stable-check",
-        "src/doc/reference/stable-check",
-    ];
-    skip.iter().any(|p| path.ends_with(p))
-}
-
 fn is_edition_2018(mut line: &str) -> bool {
     line = line.trim();
     line == "edition = \"2018\"" || line == "edition = \'2018\'"
@@ -24,7 +10,7 @@ fn is_edition_2018(mut line: &str) -> bool {
 pub fn check(path: &Path, bad: &mut bool) {
     super::walk(
         path,
-        &mut |path| filter_dirs(path) || path.ends_with("src/test"),
+        &mut |path| super::filter_dirs(path) || path.ends_with("src/test"),
         &mut |entry, contents| {
             let file = entry.path();
             let filename = file.file_name().unwrap();