Do not show empty gl-alert-actions container

What does this MR do and why?

The following discussion from !91505 (merged) should be addressed:

• @syarynovskyi started a discussion: (+2 comments)

  Looks good! I am noticing there is some extra space at the bottom of the alert container if there's a chance to clean that up here. It looks like there is an empty gl-alert-actions adding this space.

Screenshots or screen recordings

before	after

How to set up and validate locally

Set up your environment to simulate SaaS with subscriptions and enable the feature flag. Find or create group with more than 5 members and copy group path:

export GITLAB_SIMULATE_SAAS=1
bin/rails c

Feature.enable(:free_user_cap)
ApplicationSetting.first.update(check_namespace_plan: true)
Group.find_by(path: GROUP_PATH).gitlab_subscription.update(trial_ends_on: Date.yesterday)

Then go to the group Usage Quota page http://localhost:3000/groups/GROUP_PATH/-/usage_quotas#seats-quota-tab.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #366838 (closed)