stack/slapos.cfg: remove prefix 0 from version number

our shacache uploading code for pypi cannot handle the prefix 0 in the version number right now.
it will upload the version 2020.4.5.1 instead of 2020.04.05.1

stack/slapos.cfg

@@ -263,7 +263,7 @@ Werkzeug = 1.0.1
 requests = 2.27.1
 charset-normalizer = 2.0.12
 pyparsing = 2.2.0
-certifi = 2020.04.05.1
+certifi = 2020.4.5.1
 
 [versions:sys.version_info < (3,8)]
 MarkupSafe = 1.0