Update getting_started.ipynb (#4850)

minor grammer issue

docs/modules/indexes/getting_started.ipynb

@@ -7,7 +7,7 @@
    "source": [
     "# Getting Started\n",
     "\n",
-    "LangChain primary focuses on constructing indexes with the goal of using them as a Retriever. In order to best understand what this means, it's worth highlighting what the base Retriever interface is. The `BaseRetriever` class in LangChain is as follows:"
+    "LangChain primarily focuses on constructing indexes with the goal of using them as a Retriever. In order to best understand what this means, it's worth highlighting what the base Retriever interface is. The `BaseRetriever` class in LangChain is as follows:"
    ]
   },
   {