Fix use of wrong variable name

Author: rocky

xdis/bytecode.py

@@ -472,7 +472,7 @@ def get_instructions_bytes(
     varnames: tuple = code_object.co_varnames
     cellvars: tuple = code_object.co_cellvars if hasattr(code_object, "co_cellvars") else tuple()
     exception_entries = code_object.exception_entries if hasattr(code_object, "exception_entries") else tuple()
-    freevars: tuple = code_object.co_cellvars if hasattr(code_object, "co_freevars") else tuple()
+    freevars: tuple = code_object.co_freevars if hasattr(code_object, "co_freevars") else tuple()
 
     cells = cellvars + freevars