docs: Improve the tidb vector store notebook (#18773)

Remove redundant useless content, and fix some minor oversight

docs/docs/integrations/vectorstores/tidb_vector.ipynb

@@ -8,7 +8,7 @@
     "\n",
     "> [TiDB Cloud](https://tidbcloud.com/), is a comprehensive Database-as-a-Service (DBaaS) solution, that provides dedicated and serverless options. TiDB Serverless is now integrating a built-in vector search into the MySQL landscape. With this enhancement, you can seamlessly develop AI applications using TiDB Serverless without the need for a new database or additional technical stacks. Be among the first to experience it by joining the waitlist for the private beta at https://tidb.cloud/ai.\n",
     "\n",
-    "In its latest version (insert version number here), TiDB introduces support for vector search. This notebook provides a detailed guide on utilizing the TiDB Vector functionality, showcasing its features and practical applications."
+    "This notebook provides a detailed guide on utilizing the TiDB Vector functionality, showcasing its features and practical applications."
    ]
   },
   {
@@ -33,6 +33,7 @@
    "source": [
     "%pip install langchain\n",
     "%pip install langchain-openai\n",
+    "%pip install pymysql\n",
     "%pip install tidb-vector"
    ]
   },