Replace v-html with gl-sprintf in commits_header.vue

What does this MR do and why?

Replaces v-html in app/assets/javascripts/vue_merge_request_widget/components/states/commits_header.vue with gl-sprintf component which does exactly the same thing that sprintf helper function does, but in a component-friendly way.

Closes #241930 (closed).

Supersedes !41504 (closed).

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