FIX: Correctly use invite to topic email templates (#12411)

It was used both when inviting from a topic page and when creating
invites with "Send to topic on first login", while it should be used
only in the former case.

spec/mailers/invite_mailer_spec.rb

@@ -90,7 +90,7 @@ describe InviteMailer do
           Invite.find_by(invited_by_id: topic.user.id)
         end
 
-        let(:invite_mail) { InviteMailer.send_invite(invite) }
+        let(:invite_mail) { InviteMailer.send_invite(invite, invite_to_topic: true) }
 
         it 'renders the invitee email' do
           expect(invite_mail.to).to eql(['name@example.com'])