docs: Fix broken link for rate limits

Copybara import of the project:

--
02e9a6e by ahizap <67712951+ahizap@users.noreply.github.com>:

fix broken link

old link leads to 404 error

COPYBARA_INTEGRATE_REVIEW=#1360 from ahizap:main a765ff2
PiperOrigin-RevId: 904120626

Author: ahizap

codegen_instructions.md

@@ -647,4 +647,4 @@ ai.google.dev/gemini-api/docs.
 -   API Keys and Authentication: ai.google.dev/gemini-api/docs/api-key
 -   Models: ai.google.dev/models
 -   API Pricing: ai.google.dev/pricing
--   Rate Limits: ai.google.dev/rate-limits
+-   Rate Limits: ai.google.dev/gemini-api/docs/rate-limits