Lint Python notebooks with ruff. (#12677)

The new ruff version fixed the blocking bugs, and I was able to fairly
easily us to a passing state: ruff fixed some issues on its own, I fixed
a handful by hand, and I added a list of narrowly-targeted exclusions
for files that are currently failing ruff rules that we probably should
look into eventually.

I went pretty lenient on the docs / cookbooks rules, allowing dead code
and such things. Perhaps in the future we may want to tighten the rules
further, but this is already a good set of checks that found real issues
and will prevent them going forward.

docs/docs/expression_language/cookbook/code_writing.ipynb

@@ -20,8 +20,6 @@
     "from langchain.chat_models import ChatOpenAI\n",
     "from langchain.prompts import (\n",
     "    ChatPromptTemplate,\n",
-    "    SystemMessagePromptTemplate,\n",
-    "    HumanMessagePromptTemplate,\n",
     ")\n",
     "from langchain.schema.output_parser import StrOutputParser\n",
     "from langchain_experimental.utilities import PythonREPL"

docs/docs/expression_language/cookbook/multiple_chains.ipynb

@@ -69,7 +69,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from langchain.schema.runnable import RunnableMap, RunnablePassthrough\n",
+    "from langchain.schema.runnable import RunnablePassthrough\n",
     "\n",
     "prompt1 = ChatPromptTemplate.from_template(\n",
     "    \"generate a {attribute} color. Return the name of the color and nothing else:\"\n",