position .ci-action-icon-wrapper svg 0.5px higher

What does this MR do?

Positions action button's icon slightly higher in order to vertically center it correctly.

Screenshots

Before:

After:

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

Availability and Testing

Probably no risks. Tested in Chrome 78, Firefox 70 and MS Edge (Windows 10 1903).

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

Security

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team