Fixes "New label" button hit miss

What does this MR do?

The 'labels.svg' takes a fraction of a second to load after which the "New label" button shifts up a bit as seen in this video This can cause webdriver to miss the hit. With this MR, we wait for the svg to load (implicitly with has_css?) before clicking the button.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/quality/nightly/issues/59

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

Closes https://gitlab.com/gitlab-org/quality/nightly/issues/59