Use different approval icon if current user approved

What does this MR do?

Use a different approval icon if the current user approved a merge request. The alternate icon is committed here: gitlab-svgs!545 (merged)

Screenshots

First merge request is approved by someone else (original icon), second one is approved by me (and potentially others as well) \rightarrow new icon is used

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content