chore: Translate transifex_input.json in pt_PT

57% of minimum 50% translated source file: 'transifex_input.json'
on 'pt_PT'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

translations/frontend-app-course-authoring/src/i18n/messages/pt_PT.json

@@ -28,6 +28,7 @@
   "course-authoring.content-tags-drawer.spinner.loading": "A carregar",
   "course-authoring.content-tags-drawer.tags-dropdown-selector.spinner.loading": "Loading tags",
   "course-authoring.content-tags-drawer.tags-dropdown-selector.load-more-tags.button": "Load more",
+  "course-authoring.content-tags-drawer.tags-dropdown-selector.selectable-box.aria.label": "{tag} checkbox",
   "course-authoring.content-tags-drawer.content-tags-collapsible.selectable-box.selection.aria.label": "taxonomy tags selection",
   "course-authoring.course-outline.headingTitle": "Course outline",
   "course-authoring.course-outline.subTitle": "Content",