Fix a typo in README.md (persistance/persistence) (#133)

Author: musicinmybrain

README.md

@@ -3,7 +3,7 @@
 
 The Microsoft Authentication Extensions for Python offers secure mechanisms for client applications to perform cross-platform token cache serialization and persistence. It gives additional support to the [Microsoft Authentication Library for Python (MSAL)](https://github.com/AzureAD/microsoft-authentication-library-for-python).
 
-MSAL Python supports an in-memory cache by default and provides the [SerializableTokenCache](https://msal-python.readthedocs.io/en/latest/#msal.SerializableTokenCache) to perform cache serialization. You can read more about this in the MSAL Python [documentation](https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-python-token-cache-serialization). Developers are required to implement their own cache persistance across multiple platforms and Microsoft Authentication Extensions makes this simpler.
+MSAL Python supports an in-memory cache by default and provides the [SerializableTokenCache](https://msal-python.readthedocs.io/en/latest/#msal.SerializableTokenCache) to perform cache serialization. You can read more about this in the MSAL Python [documentation](https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-python-token-cache-serialization). Developers are required to implement their own cache persistence across multiple platforms and Microsoft Authentication Extensions makes this simpler.
 
 The supported platforms are Windows, Mac and Linux.
 - Windows - [DPAPI](https://docs.microsoft.com/en-us/dotnet/standard/security/how-to-use-data-protection) is used for encryption.