(maint) Enable puppetserver 8 nightlies

Nightlies for puppetserver 8 have started to ship as of
yesterday.

This commit enables the puppet7 to puppet8 upgrade test to use
puppetserver 8 nightlies.

Author: mhashizume

acceptance/helpers.rb

@@ -87,9 +87,7 @@ def require_master_collection(args)
       if args.is_a?(Symbol)
         collection = args.to_s
 
-        # Dirty, temporary workaround for when we have puppet8 agent nightlies but not server nightlies
-        # Once we have puppet8 server releases, remove the second conditional
-        unless collection.include?(server_collection) || collection == 'puppet8-nightly'
+        unless collection.include?(server_collection)
           skip_test(msg_prefix + "\nThis test requires a puppetserver from the #{collection} collection. Skipping the test ...")
         end
 

acceptance/pre_suite/00_master_setup.rb

@@ -30,14 +30,7 @@
 
   step 'Install puppetserver' do
     # puppetserver is distributed in "release streams" instead of collections.
-
-    # Dirty, temporary workaround for when we have puppet8 agent nightlies but not server nightlies
-    # Once we have puppet8 server releases, pare down to just what's in the else statement
-    opts = if install_options[:puppet_collection].include?('nightly')
-             { release_stream: 'puppet7' }
-           else
-             { release_stream: install_options[:puppet_collection] }
-           end
+    opts = { release_stream: install_options[:puppet_collection] }
 
     install_puppetserver_on(master, opts)