fix re.escape problem (#2735)

### What problem does this PR solve?

#2716

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

agent/component/generate.py

 
         kwargs["input"] = input
         for n, v in kwargs.items():
-            prompt = re.sub(r"\{%s\}" % n, re.escape(str(v)), prompt)
+            prompt = re.sub(r"\{%s\}" % re.escape(n), str(v), prompt)
 
         downstreams = self._canvas.get_component(self._id)["downstream"]
         if kwargs.get("stream") and len(downstreams) == 1 and self._canvas.get_component(downstreams[0])[