Remove space next to the icon in email button on admin/users page

changelogs/unreleased/fix-email-icon.yml

+---
+title: Remove space next to the icon in email button on admin/users page
+merge_request: 52451
+author: Yogi (@yo)
+type: fixed

ee/app/views/admin/users/_admin_email_users.html.haml

 - return unless send_emails_from_admin_area_feature_available?
 
-= link_to admin_email_path, { class: 'gl-button btn btn-default', data: { toggle: "tooltip", placement: "top", container: "body" }, title: s_("AdminUsers|Send email to users") } do
+= link_to admin_email_path, { class: 'gl-button btn btn-default btn-icon', data: { toggle: "tooltip", placement: "top", container: "body" }, title: s_("AdminUsers|Send email to users") } do
   .gl-button-icon
     = sprite_icon('mail')