docs: Remove Duplicate --quiet Flag in Installation Command in LangSm…

…ith Docs (langchain-ai#20121)

**Description:** This pull request removes a duplicated `--quiet` flag
in the pip install command found in the LangSmith Walkthrough section of
the documentation.

**Issue:** N/A

**Dependencies:** None

docs/docs/langsmith/walkthrough.ipynb

@@ -69,8 +69,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%pip install --upgrade --quiet  langchain langsmith langchainhub --quiet\n",
-    "%pip install --upgrade --quiet  langchain-openai tiktoken pandas duckduckgo-search --quiet"
+    "%pip install --upgrade --quiet  langchain langsmith langchainhub\n",
+    "%pip install --upgrade --quiet  langchain-openai tiktoken pandas duckduckgo-search"
    ]
   },
   {