Fixed incorrect classes on "Loading more results" message
Fixed incorrect classes on "Loading more results" message

This fixes an issue where the old `option` and `load-more` classes were
not switched over to the newer BEM style of class names. Unfortunately
this is a breaking change, but this is also a bug given that it doesn't
follow the proper prefixing and is likely to conflict with larger
applications.

https://github.com/select2/select2/issues/3889

tzellman/select2,tzellman/select2