stack/slapos.cfg: fix MarkupSafe version in python3.7

After the changes in 565f4986, Flask need recent version of MarkupSafe
so we must align the version of MarkupSafe and Flask.

stack/slapos.cfg

@@ -369,6 +369,7 @@ importlib-metadata = 1.7.0:whl
 itsdangerous = 0.24
 Jinja2 = 2.11.3
 jsonschema = 3.0.2:whl
+MarkupSafe = 1.0
 packaging = 16.8
 pyparsing = 2.2.0
 pyrsistent = 0.16.1
@@ -382,9 +383,6 @@ Werkzeug = 1.0.1
 wheel = 0.35.1:whl
 zipp = 1.2.0:whl
 
-[versions:sys.version_info < (3,8)]
-MarkupSafe = 1.0
-
 
 [networkcache]
 download-cache-url = http://shacache.nxdcdn.com