Fix version number

dev leading dot is automatically added.

Author: Carreau

ipykernel/_version.py

@@ -1,5 +1,5 @@
-version_info = (6, 0, 0, '.dev0')
-__version__ = '.'.join(map(str, version_info[:3]))
+version_info = (6, 0, 0, "dev0")
+__version__ = ".".join(map(str, version_info[:3]))
 
 # pep440 is annoying, beta/alpha/rc should _not_ have dots or pip/setuptools
 # confuses which one between the wheel and sdist is the most recent.