fix(GlTruncate): add aria-label when truncating in the middle

mentioned in commit 52fed23a

mentioned in merge request gitlab-svgs!1154 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!71 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!370 (merged)

mentioned in merge request status-page!903

mentioned in merge request gitlab!189863 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!372 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!373 (merged)

mentioned in merge request gitlab-svgs!1155 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!70 (merged)

mentioned in merge request gitlab!190119 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4401 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4407 (merged)

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

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1731 (merged)