removed unused 'mozmill' code

[joerg1985]

Description

Deleted the third_party/js/mozmill folder

Motivation and Context

13 years old code, not used anywhere.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[AutomatedTester]

holy moly... I had no idea that code was still in there!