Fix i18n for filter placeholder

The word `filter` needed to be translated.

ee/app/views/admin/application_settings/_required_instance_ci_setting.html.haml

@@ -19,7 +19,7 @@
       %fieldset
         .form-group
           = f.label :required_instance_ci_template, s_('AdminSettings|Select a pipeline configuration file'), class: 'text-muted'
-          = dropdown_tag(s_('AdminSettings|No required pipeline'), options: { toggle_class: 'js-ci-template-dropdown dropdown-select', title: s_('AdminSettings|Select a template'), filter: true, placeholder: "Filter", data: { data: gitlab_ci_ymls(nil) } } )
+          = dropdown_tag(s_('AdminSettings|No required pipeline'), options: { toggle_class: 'js-ci-template-dropdown dropdown-select', title: s_('AdminSettings|Select a template'), filter: true, placeholder: _("Filter"), data: { data: gitlab_ci_ymls(nil) } } )
           = f.text_field :required_instance_ci_template, value: @application_setting.required_instance_ci_template, id: 'required_instance_ci_template_name', class: 'hidden'
 
       = f.submit _('Save changes'), class: "btn btn-success"