Improve messaging for pending approval invited members

What does this MR do and why?

Improves messaging for warning group owners that the invitation is pending approval

Solves [FE] Update Error Banner to Warning Banner + Im... (#480715 - closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After
inviting_members_before	inviting_members_after

After (mobile)
inviting_members_after_iphone_se

How to set up and validate locally

1. Have an Ultimate License, and simulate Ultimate Self Managed setup (export GITLAB_SIMULATE_SAAS=0 gdk restart)
2. Enable the Setting Gitlab::CurrentSettings.update!(enable_member_promotion_management: true)
3. Enable the Feature Flag Feature.enable(:member_promotion_management)
4. Create promotion requests:
   1. Visit a group as an owner (e.g. https://gdk.test:3443/groups/gitlab-org/-/group_members)
   2. Click on invite members button
   3. Find a member. This member should have GUEST as the highest role in the hole instance. See !149094 (comment 1869616221) for details
   4. Invite them as any role higher then GUEST
   5. See the message like in the screen recordings