Animate new scroll-down icon

What does this MR do?

Recently, the scroll-up and scroll-down icons were updated. For the running test though, an SVG was used so that it could be animated. Since the SVG was based on the old icon, it was not updated. This MR updates the SVG to match the icon updates.

The animation has also been updated to be smoother and work with the new icon.

Screenshots

Before	After
Screen_Recording_2019-12-09_at_3.06.04_PM	Screen_Recording_2019-12-09_at_3.04.48_PM

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

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] 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

Closes #38378 (closed)