Make Server non-failable again

It was made failable in #382, back in 2017, as part of the
Modular Server effort that was eventually abandoned, with the
idea being that Modular Server would be blocking instead. But
when Modular Server was abandoned, we never reverted this change
to make Server non-failable again...

Signed-off-by: Adam Williamson <awilliam@redhat.com>

fedora.conf

@@ -655,9 +655,6 @@ live_media = {
 }
 
 failable_deliverables = [
-    ('^Server$', { 
-        '*': ['buildinstall', 'iso'],
-    }),
     ('^.*$', {
         # Buildinstall is non blocking
         'src': ['buildinstall'],