Set creation of a Mattermost team to unchecked as default

When creating a Mattermost group, the checkbox to create a team
for the group is set to checked by default.

app/views/groups/_create_chat_team.html.haml

@@ -6,7 +6,7 @@
       Mattermost
   .col-sm-10
     .form-check.js-toggle-container
-      .js-toggle-button.form-check-input= f.check_box(:create_chat_team, { checked: true }, true, false)
+      .js-toggle-button.form-check-input= f.check_box(:create_chat_team, { checked: false }, true, false)
       = f.label :create_chat_team, class: 'form-check-label' do
         = _('Create a Mattermost team for this group')
       %br

changelogs/unreleased/18530-disable-automatic-team-creation-mattermost.yml

+---
+title: Default the `creation of a Mattermost team` checkbox to false
+merge_request: 23329
+author: briankabiro
+type: changed

spec/features/groups_spec.rb

@@ -82,8 +82,8 @@ describe 'Group' do
           expect(page).to have_selector('#group_create_chat_team')
         end
 
-        it 'checks the checkbox by default' do
-          expect(find('#group_create_chat_team')['checked']).to eq(true)
+        it 'unchecks the checkbox by default' do
+          expect(find('#group_create_chat_team')['checked']).to eq(false)
         end
 
         it 'updates the team URL on graph path update', :js do