Minor changes

[alex-d13]

This issue collects all minor improvements

• [ ] effective richness in alpha diversity
• [ ] remove diagonal in correlation plot (optional)
• [ ] differential statistical analysis: header text size does not change with slider
• [x] Picrust2 showing top k features does not work?
• [ ] differential network: error about edge filter value appears each time
• [x] uploading namco session: works, but error message appears
• [x] check if Picrust2 descriptions are correct for EC and KO; might be mixed up..

[alex-d13]

• [x] differential analysis: associations --> user was not able to download PDF
• [ ] phylogenetic analysis: cladogram --> user was not able to download PDF