Remove obsolete CSS and fix icon alignment

What does this MR do?

This MR removes CSS which causes misaligned icon in reports (displayed on merge requests page)

GitLab.com	Local after fix

It also removes styling of .loading-container which is blocking us from getting new gl-spinner styles merged

Does this MR meet the acceptance criteria?

Conformity

• [ - ] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [ - ] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [ - ] Database guides
• [ - ] Separation of EE specific content

Performance and Testing

• [ - ] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers