Adds gitlab-credits icon

What does this MR do?

Adds gitlab-credits icon.

Relates to https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/work_items/3206

Screenshots or screen recordings

Integrations

NA

Does this MR meet the acceptance criteria?

This checklist encourages the authors, reviewers, and maintainers of merge requests (MRs) to confirm changes were analyzed for conformity with the project's guidelines, security and accessibility.

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Conformity

• The “What does this MR do?” section in the MR description is filled out, explaining the reasons for and scope of the proposed changes, per “Say why not just what”.
  • For example, if the MR is focused on usage guidelines, addressing accessibility challenges could be added in a separate MR.
• Relevant label(s) are applied to the MR.
• The MR is added to a milestone.
• Added the ~"component:*" label(s) if applicable.
• A changeset is added when this MR will do a patch, minor, or major update. More information can be found in doc/publishing-packages.md.

Components

• GitLab UI's contributing guidelines.
• If the MR changes a component's API, integration MR(s) have been opened (see integrations above).

Documentation

• If creating a new component page from scratch, it follows the page template structure.
• Content follows the Pajamas voice and tone guidelines, falling back on the GitLab Documentation Style Guide when needed.
• Related pages are cross-linked, where helpful. Component pages have related components and patterns defined in their Markdown front matter.
• If embedding a Figma file, it follows the Figma embed guide.
• Review requested from any GitLab designer or directly from a maintainer or trainee maintainer.
• Maintainer review follows the Pajamas UX maintainer review checklist.

Security

NA

Accessibility

NA