Fix env var typo (#1322)

livekit-plugins/livekit-plugins-google/livekit/plugins/google/beta/realtime/realtime_api.py

@@ -105,7 +105,7 @@ def __init__(
 
         Args:
             instructions (str, optional): Initial system instructions for the model. Defaults to "".
-            api_key (str or None, optional): OpenAI API key. If None, will attempt to read from the environment variable OPENAI_API_KEY
+            api_key (str or None, optional): Google Gemini API key. If None, will attempt to read from the environment variable GOOGLE_API_KEY.
             modalities (ResponseModality): Modalities to use, such as ["TEXT", "AUDIO"]. Defaults to ["AUDIO"].
             model (str or None, optional): The name of the model to use. Defaults to "gemini-2.0-flash-exp".
             voice (api_proto.Voice, optional): Voice setting for audio outputs. Defaults to "Puck".