fix: Update .env.example for Gemini Live

Author: tjirab

examples/other_examples/gemini_live_realtime/.env.example

@@ -3,5 +3,6 @@ STREAM_API_KEY=your_stream_api_key_here
 STREAM_API_SECRET=your_stream_api_secret_here
 EXAMPLE_BASE_URL=https://pronto.getstream.io
 
-# Deepgram API credentials
-DEEPGRAM_API_KEY=your_deepgram_api_key_here
+# Google/Gemini
+# Get your key from: https://aistudio.google.com/app/apikey
+GOOGLE_API_KEY=your_google_gemini_key