Adopt let else in more places

compiler/rustc_lint/src/context.rs

@@ -278,9 +278,8 @@ impl LintStore {
     /// This lint has been renamed; warn about using the new name and apply the lint.
     #[track_caller]
     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
-        let target = match self.by_name.get(new_name) {
-            Some(&Id(lint_id)) => lint_id,
-            _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
+        let Some(&Id(target)) = self.by_name.get(new_name) else {
+            bug!("invalid lint renaming of {} to {}", old_name, new_name);
         };
         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
     }