Prevent adding of tags vocabulary to debut features with tags fields

Due to a recent change, Features by design adds a vocabulary, or a dependency on a feature module providing that vocabulary, to any feature containing a field that references that vocabulary.

In Debut, we have opted to create the tags vocabulary on install in each feature using tags, to avoid creating a dependency on a debut_tags feature.

To avoid the tags vocabulary being added, we need to implement hook_features_export_alter() to remove it from the export.