Hi!
I found on this forum and a little changed this way to fix it:
!qiime feature-classifier classify-sklearn \
--i-classifier training-feature-classifiers/classifier.qza \
--i-reads rep-seqs.qza \
--o-classification taxonomy.qza
!qiime tools export \
--input-path taxonomy.qza \
--output-path taxonomy-with-spaces
!qiime metadata tabulate \
--m-input-file taxonomy-with-spaces/taxonomy.tsv \
--o-visualization taxonomy-as-metadata.qzv
!qiime tools export \
--input-path taxonomy-as-metadata.qzv \
--output-path taxonomy-as-metadata
!qiime tools import \
--type 'FeatureData[Taxonomy]' \
--input-path taxonomy-as-metadata/metadata.tsv \
--output-path taxonomy-without-spaces.qza
!qiime metadata tabulate \
--m-input-file taxonomy-without-spaces.qza \
--o-visualization taxonomy-without-spaces.qzv