Update requirements.txt

Updated docutils version req because docs failed with the following message:

The conflict is caused by:
    The user requested docutils==0.12
    sphinx 5.0.2 depends on docutils<0.19 and >=0.14

docs/requirements.txt

@@ -1,6 +1,6 @@
 sphinx==5.0.2
 sphinxcontrib-napoleon
-docutils==0.12
+docutils>=0.14
 sphinx_rtd_theme
 sphinx-argparse
 snakemake>=5.32.0,<6.5.0