Add missing comma in code sample

Author: CaroFG

guides/embedders/gemini.mdx

@@ -32,7 +32,7 @@ Here's an example of embedder settings for Gemini:
     "headers": {
     "Content-Type": "application/json",
     "x-goog-api-key": "<Google API Key>"
-    }
+    },
     "url": "https://generativelanguage.googleapis.com/v1beta/models/gemini-embedding-001:batchEmbedContents",
     "request": {
     "requests": [