Merge branch '225206-replace-fa-book-icon-with-gitlab-svg-book-icon' into 'master'

Replace fa-book icon with GitLab SVG book icon

See merge request gitlab-org/gitlab!39247

app/views/projects/blob/viewers/_contributing.html.haml

-= icon('book fw')
+= sprite_icon('book')
 After you've reviewed these contribution guidelines, you'll be all set to
 
 - options = contribution_options(viewer.project)

changelogs/unreleased/225206-replace-fa-book-icon-with-gitlab-svg-book-icon.yml

+---
+title: Replace fa-book icon with GitLab SVG book icon
+merge_request: 39247
+author:
+type: changed