docs: Fix Memgraph class name (#31329)

- **Description:** Fix Memgraph name that has been changed in the
integration.

Author: antejavor

docs/docs/integrations/graphs/memgraph.ipynb

@@ -65,14 +65,16 @@
     "\n",
     "from langchain_core.prompts import PromptTemplate\n",
     "from langchain_memgraph.chains.graph_qa import MemgraphQAChain\n",
-    "from langchain_memgraph.graphs.memgraph import Memgraph\n",
+    "from langchain_memgraph.graphs.memgraph import MemgraphLangChain\n",
     "from langchain_openai import ChatOpenAI\n",
     "\n",
     "url = os.environ.get(\"MEMGRAPH_URI\", \"bolt://localhost:7687\")\n",
     "username = os.environ.get(\"MEMGRAPH_USERNAME\", \"\")\n",
     "password = os.environ.get(\"MEMGRAPH_PASSWORD\", \"\")\n",
     "\n",
-    "graph = Memgraph(url=url, username=username, password=password, refresh_schema=False)"
+    "graph = MemgraphLangChain(\n",
+    "    url=url, username=username, password=password, refresh_schema=False\n",
+    ")"
    ]
   },
   {

docs/docs/integrations/providers/memgraph.mdx

@@ -14,7 +14,7 @@ and use them to retrieve relevant information from the database.
 
 ```python
 from langchain_memgraph.chains.graph_qa import MemgraphQAChain
-from langchain_memgraph.graphs.memgraph import Memgraph
+from langchain_memgraph.graphs.memgraph import MemgraphLangChain
 ```
 
 See a [usage example](/docs/integrations/graphs/memgraph)
@@ -24,7 +24,7 @@ See a [usage example](/docs/integrations/graphs/memgraph)
 You can use the integration to construct a knowledge graph from unstructured data.
 
 ```python
-from langchain_memgraph.graphs.memgraph import Memgraph
+from langchain_memgraph.graphs.memgraph import MemgraphLangChain
 from langchain_experimental.graph_transformers import LLMGraphTransformer
 ```
 

docs/docs/integrations/tools/memgraph.ipynb

@@ -87,9 +87,9 @@
    "source": [
     "from langchain.chat_models import init_chat_model\n",
     "from langchain_memgraph import MemgraphToolkit\n",
-    "from langchain_memgraph.graphs.memgraph import Memgraph\n",
+    "from langchain_memgraph.graphs.memgraph import MemgraphLangChain\n",
     "\n",
-    "db = Memgraph(url=url, username=username, password=password)\n",
+    "db = MemgraphLangChain(url=url, username=username, password=password)\n",
     "\n",
     "llm = init_chat_model(\"gpt-4o-mini\", model_provider=\"openai\")\n",
     "\n",