Enable SDG content by default

We didn't enable it by default in commit 676adfcb3 so existing
installations didn't suddenly get a new section without expecting it.

But since the setting already exists for installations using version
CONSUL 1.3, now it will only be enabled for new installations.

app/models/setting.rb

@@ -100,7 +100,7 @@ class Setting < ApplicationRecord
         "feature.remote_census": nil,
         "feature.valuation_comment_notification": true,
         "feature.graphql_api": true,
-        "feature.sdg": false,
+        "feature.sdg": true,
         "feature.machine_learning": false,
         "homepage.widgets.feeds.debates": true,
         "homepage.widgets.feeds.processes": true,

db/dev_seeds/settings.rb

@@ -5,7 +5,6 @@ section "Creating Settings" do
     "facebook_handle": "CONSUL",
     "feature.featured_proposals": "true",
     "feature.map": "true",
-    "feature.sdg": "true",
     "instagram_handle": "CONSUL",
     "mailer_from_address": "noreply@consul.dev",
     "mailer_from_name": "CONSUL",