Resolve extra space in Child and Linked items widgets

What does this MR do and why?

This MR is extension of Reflow work item layout on small screens (!142776 - merged).

• Fixes the extra space in Child items and Linked items widgets
• Fixes the Color widget truncation on Epic work items

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

Child items and Linked Items spacing issue

Before	After

Color widget issue:

Before	After

How to set up and validate locally

Prerequisites:

1. Enable the OKRs feature as mentioned in the OKRs docs (e.g. ::Feature.enabled?(:okrs_mvc, Project.find(<PROJECT_ID>)) and the namespace must have Ultimate plan).
2. Enable ::Feature.enabled?(:work_items_mvc_2, Project.find(<PROJECT_ID>))

Steps to verify Child items and Linked Items spacing issue:

1. Login with any user
2. Go to any Project > Issues > List
3. Create an new Objective under New issue split button
4. Go to Objective detail page
5. Check with the Child items and Linked items widget.
6. Check in mobile view if it is looking good

Steps to verify Color widget issue:

1. Login with any user
2. Go to any Group > Epic
3. Change the URL from /epics to /work_items e.g. http://127.0.0.1:3000/groups/gitlab-org/-/epics > http://127.0.0.1:3000/groups/gitlab-org/-/work_items
4. Create an new Epic work item
5. Go to the Epic work item detail page
6. Interact with the Color widget

Related to #440693 (closed)