Removed user_library_material_manaagers_directory_path property.

Removed from ScoreManagerConfiguration.

FILESYSTEM: you may remove any managers/ directory in your score manager
library.

No longer used.

Any collaterla housed in your managers/ directory can be moved to your makers/
directory instead.
Removed abjad_material_managers_directory_path property.

Removed from ScoreManagerConfiguration.

No longer needed.