Enable `terms_of_service_vue` feature flag by default

Set max-height on terms of service so accept and decline buttons are
always visible. Also disable accept button until user scrolls to the
bottom of the terms of service.

Changelog: changed

config/feature_flags/development/terms_of_service_vue.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/343046
 milestone: '14.5'
 type: development
 group: group::access
-default_enabled: false
+default_enabled: true