Replace v-html with v-safe-html in header_ci_component.vue

What does this MR do?

This MR replaces v-html with v-safe-html in app/assets/javascripts/vue_shared/components/header_ci_component.vue.

Relates to #241896 (closed).

Steps to test/replicate

1. Go to any pipeline that was triggered by a user with a status emoji set (at the time of testing).
2. See the emoji. It is actually raw HTML that is passed to the header_ci_component (through the user object) but it should render fine because there is no unsafe HTML.

Also in the DevTools

Screenshots

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
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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