chore: fix flake8 error

Author: samineer

src/fluent_compiler/codegen.py

@@ -675,7 +675,7 @@ def as_ast(self):
         return ast.Name(id=self.name, ctx=ast.Load(), **DEFAULT_AST_ARGS)
 
     def __eq__(self, other):
-        return type(other) == type(self) and other.name == self.name
+        return isinstance(other, type(self)) and other.name == self.name
 
     def __repr__(self):
         return f"VariableReference({repr(self.name)})"