Bump some Python dependencies

requirements.txt

@@ -1,6 +1,6 @@
-Jinja2==3.0.0
-minicli==0.4.4
-mistune==2.0.0a5
-Pillow==7.1.2
-python-slugify==4.0.0
-regex==2020.11.13
+Jinja2==3.0.1
+minicli==0.5.0
+mistune==2.0.0rc1
+Pillow==8.3.1
+python-slugify==5.0.2
+regex==2021.8.3