Remove alert styles

[janfaracik]

With jenkinsci/jenkins#9115 it's no longer necessary for themes to set alert style variables - so this merge request removes them.

Can either have the minimum Jenkins version be set to the weekly that contains the above MR or I can set the variables here with a comment that they can eventually be removed.

Before 9115

After 9115

Testing done

Submitter checklist

Edit tasklist title

Beta Give feedback Tasklist Submitter checklist, more options

• Rename
• Copy markdown
• Delete tasklist

Delete tasklist

Delete tasklist block?

Are you sure? All relationships in this tasklist will be removed.

Cancel Delete

1. Make sure you are opening from a **topic/feature/bugfix branch** (right side) and not your main branch!

   Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove
2. Ensure that the pull request title represents the desired changelog entry

   Ensure that the pull request title represents the desired changelog entry
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove
3. Please describe what you did

   Please describe what you did
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove
4. Link to relevant issues in GitHub or Jira

   Link to relevant issues in GitHub or Jira
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove
5. Link to relevant pull requests, esp. upstream and downstream changes

   Link to relevant pull requests, esp. upstream and downstream changes
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

   Ensure you have provided tests - that demonstrates feature works or fixes the issue
   Options

   • Convert to issue
   • Toggle completion
   • Rename
   • Remove

Add item to Submitter checklist

[timja]

I've added a screenshot, I think update the minimum version is best for maintenance.

[janfaracik]

Updated it to point to the latest weekly with the relevant alert style changes.