Fix gl-icon in ee/app/assets/javascripts/vue_shared/dashboards/components/alerts.vue

from !173401 (comment 2226258651)

The icon on line 35 is designed for use at size 16

For more information look at the gl-icon storybook entry: https://gitlab-org.gitlab.io/gitlab-ui/?path=/docs/base-icon--docs

Implementation Guide: change size to 16 Make sure to add screenshots to MR