docs: update LangSmith links (#32070)

Author: lnhsingh

docs/docs/how_to/index.mdx

@@ -362,14 +362,14 @@ relevant to LangChain below:
 Evaluating performance is a vital part of building LLM-powered applications.
 LangSmith helps with every step of the process from creating a dataset to defining metrics to running evaluators.
 
-To learn more, check out the [LangSmith evaluation how-to guides](https://docs.smith.langchain.com/how_to_guides#evaluation).
+To learn more, check out the [LangSmith evaluation how-to guides](https://docs.smith.langchain.com/evaluation/how_to_guides).
 
 ### Tracing
 <span data-heading-keywords="trace,tracing"></span>
 
 Tracing gives you observability inside your chains and agents, and is vital in diagnosing issues.
 
-- [How to: trace with LangChain](https://docs.smith.langchain.com/how_to_guides/tracing/trace_with_langchain)
-- [How to: add metadata and tags to traces](https://docs.smith.langchain.com/how_to_guides/tracing/trace_with_langchain#add-metadata-and-tags-to-traces)
+- [How to: trace with LangChain](https://docs.smith.langchain.com/observability/how_to_guides/trace_with_langchain)
+- [How to: add metadata and tags to traces](https://docs.smith.langchain.com/observability/how_to_guides/add_metadata_tags)
 
-You can see general tracing-related how-tos [in this section of the LangSmith docs](https://docs.smith.langchain.com/how_to_guides/tracing).
+You can see general tracing-related how-tos [in this section of the LangSmith docs](https://docs.smith.langchain.com/observability/how_to_guides#tracing-configuration).