Work items in modal have extra trailing timeline connector in dark mode

Summary

Everyone's favorite bug 🐛

Steps to reproduce

  1. Enable dark mode in Preferences
  2. Open a work item in a modal (e.g. open a task from an issue)

Example Project

gitlab

What is the current bug behavior?

Connector line in last note is visible with nothing to connect to

What is the expected correct behavior?

No visible connector line on last note

Relevant logs and/or screenshots

Light mode ✅ Dark mode 🚫 Full page ✅
image image image

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info 

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check 
(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)


(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)


(we will only investigate if the tests are passing)

Possible fixes