[Clang][NFC] use const references for function parameters in operator== and operator!= overloads in Redeclarable.h (#92963)

Fixes #92755

Author: a-tarasyuk

clang/include/clang/AST/Redeclarable.h

@@ -281,10 +281,10 @@ class Redeclarable {
       return tmp;
     }
 
-    friend bool operator==(redecl_iterator x, redecl_iterator y) {
+    friend bool operator==(const redecl_iterator &x, const redecl_iterator &y) {
       return x.Current == y.Current;
     }
-    friend bool operator!=(redecl_iterator x, redecl_iterator y) {
+    friend bool operator!=(const redecl_iterator &x, const redecl_iterator &y) {
       return x.Current != y.Current;
     }
   };