Fix broken environments terminal

This addresses the missing stylesheet which caused unexpected behavior in the environments terminal.

When loading the terminal on the environments page, the css needed for the terminal to display correctly wasn't loading. This MR addresses this problem by loading the css missing css file in the environments page.

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/64091

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines