Fix is_keyword_ahead visibility

Co-authored-by: Takayuki Maeda <takoyaki0316@gmail.com>

compiler/rustc_parse/src/parser/mod.rs

@@ -1115,7 +1115,7 @@ pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R
     }
 
     /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
-    pub fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
+    pub(crate) fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
         self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
     }