chore(js/plugins/google-genai): Update error message URL for API key instructions

https://genkit.dev/docs/integrations/google-genai

Author: pavelgj

js/plugins/google-genai/src/vertexai/utils.ts

@@ -294,7 +294,7 @@ export const MISSING_API_KEY_ERROR = new GenkitError({
   status: 'FAILED_PRECONDITION',
   message:
     'Please pass in the API key or set the VERTEX_API_KEY or GOOGLE_API_KEY environment variable.\n' +
-    'For more details see https://firebase.google.com/docs/genkit/plugins/google-genai',
+    'For more details see https://genkit.dev/docs/integrations/google-genai',
 });
 
 export const API_KEY_FALSE_ERROR = new GenkitError({