Use simple list type for encrypt_groups site setting

Use simple list type for encrypt_groups site setting

diff --git a/config/settings.yml b/config/settings.yml
index 839c1ab..a0b2e74 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -11,3 +11,4 @@ plugins:
     default: ""
     client: true
     type: list
+    list_type: simple

GitHub sha: 5d42b1ed