message: chore(README): preprint -> paper
diff: @@ -191,7 +191,7 @@ by Nextstrain team
  If you use results obtained with Nextclade in a publication, please
  - - cite our preprint:
  + - cite our paper:
  > Aksamentov, I., Roemer, C., Hodcroft, E. B., & Neher, R. A., (2021). Nextclade: clade assignment, mutation calling and quality control for viral genomes. Journal of Open Source Software, 6(67), 3773, https://doi.org/10.21105/joss.03773
  