docs: standardize vertexai params (#20167)

Related to #20085

Requires https://github.com/langchain-ai/langchain-google/pull/121

cookbook/Multi_modal_RAG_google.ipynb

@@ -185,7 +185,7 @@
     "    )\n",
     "    # Text summary chain\n",
     "    model = VertexAI(\n",
-    "        temperature=0, model_name=\"gemini-pro\", max_output_tokens=1024\n",
+    "        temperature=0, model_name=\"gemini-pro\", max_tokens=1024\n",
     "    ).with_fallbacks([empty_response])\n",
     "    summarize_chain = {\"element\": lambda x: x} | prompt | model | StrOutputParser()\n",
     "\n",
@@ -254,7 +254,7 @@
     "\n",
     "def image_summarize(img_base64, prompt):\n",
     "    \"\"\"Make image summary\"\"\"\n",
-    "    model = ChatVertexAI(model_name=\"gemini-pro-vision\", max_output_tokens=1024)\n",
+    "    model = ChatVertexAI(model=\"gemini-pro-vision\", max_tokens=1024)\n",
     "\n",
     "    msg = model.invoke(\n",
     "        [\n",
@@ -553,9 +553,7 @@
     "    \"\"\"\n",
     "\n",
     "    # Multi-modal LLM\n",
-    "    model = ChatVertexAI(\n",
-    "        temperature=0, model_name=\"gemini-pro-vision\", max_output_tokens=1024\n",
-    "    )\n",
+    "    model = ChatVertexAI(temperature=0, model_name=\"gemini-pro-vision\", max_tokens=1024)\n",
     "\n",
     "    # RAG pipeline\n",
     "    chain = (\n",

docs/docs/integrations/chat/google_vertex_ai_palm.ipynb

@@ -114,7 +114,7 @@
     "human = \"Translate this sentence from English to French. I love programming.\"\n",
     "prompt = ChatPromptTemplate.from_messages([(\"system\", system), (\"human\", human)])\n",
     "\n",
-    "chat = ChatVertexAI(model_name=\"gemini-pro\", convert_system_message_to_human=True)\n",
+    "chat = ChatVertexAI(model=\"gemini-pro\", convert_system_message_to_human=True)\n",
     "\n",
     "chain = prompt | chat\n",
     "chain.invoke({})"
@@ -233,9 +233,7 @@
     }
    ],
    "source": [
-    "chat = ChatVertexAI(\n",
-    "    model_name=\"codechat-bison\", max_output_tokens=1000, temperature=0.5\n",
-    ")\n",
+    "chat = ChatVertexAI(model=\"codechat-bison\", max_tokens=1000, temperature=0.5)\n",
     "\n",
     "message = chat.invoke(\"Write a Python function generating all prime numbers\")\n",
     "print(message.content)"
@@ -399,7 +397,7 @@
     "    location: str = Field(..., description=\"The city and state, e.g. San Francisco, CA\")\n",
     "\n",
     "\n",
-    "llm = ChatVertexAI(model_name=\"gemini-pro\", temperature=0)\n",
+    "llm = ChatVertexAI(model=\"gemini-pro\", temperature=0)\n",
     "llm_with_tools = llm.bind_tools([GetWeather])\n",
     "ai_msg = llm_with_tools.invoke(\n",
     "    \"what is the weather like in San Francisco\",\n",
@@ -551,7 +549,7 @@
     "human = \"{text}\"\n",
     "prompt = ChatPromptTemplate.from_messages([(\"system\", system), (\"human\", human)])\n",
     "\n",
-    "chat = ChatVertexAI(model_name=\"chat-bison\", max_output_tokens=1000, temperature=0.5)\n",
+    "chat = ChatVertexAI(model=\"chat-bison\", max_tokens=1000, temperature=0.5)\n",
     "chain = prompt | chat\n",
     "\n",
     "asyncio.run(\n",

docs/docs/integrations/llms/google_vertex_ai_palm.ipynb

@@ -403,7 +403,7 @@
     }
    ],
    "source": [
-    "llm = VertexAI(model_name=\"code-bison\", max_output_tokens=1000, temperature=0.3)\n",
+    "llm = VertexAI(model_name=\"code-bison\", max_tokens=1000, temperature=0.3)\n",
     "question = \"Write a python function that checks if a string is a valid email address\"\n",
     "print(model.invoke(question))"
    ]
@@ -439,7 +439,7 @@
     "from langchain_core.messages import HumanMessage\n",
     "from langchain_google_vertexai import ChatVertexAI\n",
     "\n",
-    "llm = ChatVertexAI(model_name=\"gemini-pro-vision\")\n",
+    "llm = ChatVertexAI(model=\"gemini-pro-vision\")\n",
     "\n",
     "image_message = {\n",
     "    \"type\": \"image_url\",\n",