fix(llmobs): enable gemini on LLM Obs enable (#10849)

This PR makes sure the gemini integration is enabled after calling
`LLMObs.enable()`
Want this to be backported to 2.14 since that's when gemini will be
shipped

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## Reviewer Checklist
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---------

Co-authored-by: lievan <[email protected]>

ddtrace/llmobs/_llmobs.py

@@ -64,6 +64,7 @@
     "bedrock": "botocore",
     "openai": "openai",
     "langchain": "langchain",
+    "google_generativeai": "google_generativeai",
 }
 
 

releasenotes/notes/add-google-genai-to-llm-integrations-20bc03131f624e42.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    LLM Observability: This fix resolves an issue where LLMObs.enable() did not patch google_generativeai library.