hid the Add/Sync Subscriber options - default behavior is now always 'sync' (version 5.2)

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894813 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated first screenshot

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894863 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated screenshot 2

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894980 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated screenshot 3

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894994 b8457f37-d9ea-0310-8a92-e5e31aec5664