classify-otus-experimental tutorial data files are missing

[nbokulich]

Bug Description
The tutorial (recently moved to the QIIME 2 library) cites a taxonomy_gg99.qza file link that is broken.

Steps to reproduce the behavior
See "assign taxonomy" tutorial here: https://library.qiime2.org/plugins/q2-fragment-insertion/16/

Expected behavior
File should be replaced here, or the link fixed to point elsewhere in the tutorial (probably a better solution).

References
forum xref

[thermokarst]

Thanks @nbokulich! I removed the taxonomy assignment section from the tutorial for now.