[BUG] List variable inputs aren't interpreted for python nodes

[axecopfire]

Describe the bug Input variables are not being interpolated for python node inputs.

How To Reproduce the bug

- name: process_topic
  type: python
  source:
    type: code
    path: src/process_detected_topics.py
  inputs:
    topics:
    - ${topic_detection_1.output}
    - ${topic_detection_2.output}

Results in the input for topics: ["${topic_detection_1.output}","${topic_detection_2.output}"].

Expected behavior topic_detection_[N].output should be interpolated to the output values of those nodes.

Screenshots If applicable, add screenshots to help explain your problem.

Running Information(please complete the following information):

• Promptflow Package Version using pf -v: [e.g. 0.0.102309906]
• Operating System: [e.g. Ubuntu 20.04, Windows 11]
• Python Version using python --version: [e.g. python==3.10.12]

Additional context Add any other context about the problem here.