Typo fix

Author: munrojm

mp_api/client/core/client.py

@@ -74,7 +74,7 @@ def __init__(
         headers: dict = None,
         mute_progress_bars: bool = settings.MUTE_PROGRESS_BARS,
     ):
-        """Initialise the REST API helper class.
+        """Initialize the REST API helper class.
 
         Arguments:
             api_key: A String API key for accessing the MaterialsProject