Enable snippets for new projects by default

If there is an existing gitlab.yml file with snippets explicitly
disabled, they won't be enabled with this change.

changelogs/unreleased/enable-snippets-by-default.yml

+---
+title: Enable snippets for new projects by default
+merge_request:
+author:

config/gitlab.yml.example

@@ -89,7 +89,7 @@ production: &base
       issues: true
       merge_requests: true
       wiki: true
-      snippets: false
+      snippets: true
       builds: true
       container_registry: true
 

config/initializers/1_settings.rb

@@ -221,7 +221,7 @@ Settings.gitlab['session_expire_delay'] ||= 10080
 Settings.gitlab.default_projects_features['issues']             = true if Settings.gitlab.default_projects_features['issues'].nil?
 Settings.gitlab.default_projects_features['merge_requests']     = true if Settings.gitlab.default_projects_features['merge_requests'].nil?
 Settings.gitlab.default_projects_features['wiki']               = true if Settings.gitlab.default_projects_features['wiki'].nil?
-Settings.gitlab.default_projects_features['snippets']           = false if Settings.gitlab.default_projects_features['snippets'].nil?
+Settings.gitlab.default_projects_features['snippets']           = true if Settings.gitlab.default_projects_features['snippets'].nil?
 Settings.gitlab.default_projects_features['builds']             = true if Settings.gitlab.default_projects_features['builds'].nil?
 Settings.gitlab.default_projects_features['container_registry'] = true if Settings.gitlab.default_projects_features['container_registry'].nil?
 Settings.gitlab.default_projects_features['visibility_level']   = Settings.send(:verify_constant, Gitlab::VisibilityLevel, Settings.gitlab.default_projects_features['visibility_level'], Gitlab::VisibilityLevel::PRIVATE)