fix(GlAreaChart): Legend is updated on changes

mentioned in commit 2f9eecba

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1630 (merged)

mentioned in merge request status-page!903

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!67 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!367 (merged)

mentioned in merge request gitlab!186516 (merged)

mentioned in merge request gitlab-svgs!1125 (merged)

mentioned in merge request gitlab-svgs!1126 (merged)

mentioned in merge request gitlab!186687 (closed)

mentioned in merge request gitlab-svgs!1127 (closed)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1638 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4368 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4369 (merged)

mentioned in merge request gitlab-org/technical-writing/docs-gitlab-com!682 (closed)

mentioned in merge request gitlab-org/technical-writing/docs-gitlab-com!683 (merged)