Fix OpenAI cross-encoder prompt

[prasmussen15]

[!IMPORTANT] Fix order of query and passage in rank() function's message content in openai_reranker_client.py.

• Behavior:
  • Fix order of query and passage in rank() function's message content in openai_reranker_client.py.
• Misc:
  • Adjust indentation in rank() function in openai_reranker_client.py.

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