Fixing tags at webapp creation

The tags aren't mandatory at the creation as noted by @abaire

. I added
the argument `required=False` in order to correct it.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

django/allgo/main/forms.py

@@ -157,7 +157,7 @@ class WebappForm(forms.ModelForm):
             help_text=mark_safe('This is the <a href="https://allgo.gitlabpages.inria.fr/doc/deploy.html#entrypoint">command executed when allgo runs a job</a> for this app.'),
             initial="/home/allgo/entrypoint")
     owner = forms.CharField(required=False, label="Owner", label_suffix='', help_text="Username of the new owner of the application. You will immediately loose access to the application.")
-    tags = TagField(label_suffix='', help_text="Tags are separated by a comma.")
+    tags = TagField(required=False, label_suffix='', help_text="Tags are separated by a comma.")
 
     def __init__(self, *args, **kwargs):
         super(WebappForm, self).__init__(*args, **kwargs)