Allow developer role to access group-level templates

Previously only maintainer and above roles were able to
create projects using group level templates.
As per our documentation, group level templates should be
accessible to any roles that has access to create new projects.
Lowering the bar to allow developer role to create projects
using group-level templates.

ee/app/models/ee/user.rb

@@ -181,7 +181,7 @@ module EE
     def available_subgroups_with_custom_project_templates(group_id = nil)
       groups = GroupsWithTemplatesFinder.new(group_id).execute
 
-      GroupsFinder.new(self, min_access_level: ::Gitlab::Access::MAINTAINER)
+      GroupsFinder.new(self, min_access_level: ::Gitlab::Access::DEVELOPER)
                   .execute
                   .where(id: groups.select(:custom_project_templates_group_id))
                   .includes(:projects)

ee/spec/models/user_spec.rb

@@ -364,7 +364,7 @@ describe User do
 
       context 'when the access level of the user is below the required one' do
         before do
-          group_1.add_developer(user)
+          group_1.add_reporter(user)
         end
 
         it 'returns an empty collection' do
@@ -374,9 +374,9 @@ describe User do
 
       context 'when the access level of the user is the correct' do
         before do
-          group_1.add_maintainer(user)
+          group_1.add_developer(user)
           group_2.add_maintainer(user)
-          group_3.add_maintainer(user)
+          group_3.add_developer(user)
         end
 
         context 'when a Group ID is passed' do