revert: spelling adjustment in examples/

1. a -> an in getting-started-with-redis-and-openai.ipynb

examples/vector_databases/redis/getting-started-with-redis-and-openai.ipynb

@@ -692,7 +692,7 @@
     "\n",
     "``HNSW`` will take longer to build and consume more memory for most cases than ``FLAT`` but will be faster to run queries on, especially for large datasets.\n",
     "\n",
-    "The following cells will show how to create a ``HNSW`` index and run queries with it using the same data as before."
+    "The following cells will show how to create an ``HNSW`` index and run queries with it using the same data as before."
    ]
   },
   {