Chracter Splitting's llama index's imports aren't working; update them with new working imports

[maharun0]

❌ Problem:

Chracter Splitting's llama index's imports aren't working;

File location: 5_Levels_Of_Text_Splitting.ipynb

✅ Solution:

Replace them with following lines:

from llama_index.core.node_parser import SentenceSplitter
from llama_index.core import SimpleDirectoryReader