mds: operator=() should return 'CDentry&'

Fixes: https://tracker.ceph.com/issues/73419
Signed-off-by: Edwin Rodriguez <[email protected]>

Author: edwinzrodriguez

src/mds/CDentry.h

@@ -250,7 +250,7 @@ class CDentry : public MDSCacheObject, public LRUObject, public Counter<CDentry>
 
   // copy cons
   CDentry(const CDentry& m);
-  const CDentry& operator= (const CDentry& right);
+  CDentry& operator=(const CDentry& right) = delete;
 
   // misc
   void make_trimmed_path_string(std::string& s, bool projected,