Fixes duplicate api key being passed in openrouter.py (#1216)

* Updated documentation for pip install in zsh

Fixes #1209

Updated documentation to handle installation using `zsh` on Macs, which is now the default shell.

* Update openrouter.py

packages/jupyter-ai-magics/jupyter_ai_magics/partner_providers/openrouter.py

@@ -36,7 +36,7 @@ def __init__(self, **kwargs):
         openrouter_api_base = kwargs.pop(
             "openai_api_base", "https://openrouter.ai/api/v1"
         )
-
+        kwargs.pop("openrouter_api_key", None)
         super().__init__(
             openai_api_key=openrouter_api_key,
             openai_api_base=openrouter_api_base,