Update ExtensionArray.interpolate to remove outdated method of pad
Removed the outdated method of `pad` from ExtensionArray.interpolate.

Reason:

- Found in #59749 that `pad` raises a ValueError whatever value you pass. 
- #57092) says that `pad` has been removed from DataFrame.Interpolate, which is the origin of ExtensionArray. 

Thanks @ammar-qazi 