Deprecated `scrollbar_thumb.background` usage

[maxdeviant]

This extension has been identified as using the deprecated scrollbar_thumb.background style property.

This property has been deprecated in favor of scrollbar.thumb.background. Please migrate to using the new property.

The following themes are impacted:

• Theme "Hacker Night Vision Dark" is using deprecated style property scrollbar_thumb.background
• Theme "Hacker Night Vision Dark Force" is using deprecated style property scrollbar_thumb.background
• Theme "Hacker Night Vision Dark Blackops" is using deprecated style property scrollbar_thumb.background
• Theme "Hacker Night Vision Dark Operator" is using deprecated style property scrollbar_thumb.background
• Theme "Hacker Night Vision Light" is using deprecated style property scrollbar_thumb.background

[davccavalcante]

• Hacker Night

Done