Fixes "modified at" metadata of file contents

tracim/tracim/i18n/fr/LC_MESSAGES/tracim.po

 #: tracim/lib/app_globals.py:26
 #, python-format
 msgid "%B %d at %I:%M%p"
-msgstr "le %d %B à %H:%M"
+msgstr "%d %B à %H:%M"
 
 #: tracim/lib/calendar.py:45
 msgid "My personal calendar"

tracim/tracim/templates/file/getone.mak

                     selectedRevision: '${result.file.selected_revision}',
                     weight: '${h.user_friendly_file_size(result.file.file.size)}',
                     height: '300',
-                    modifiedAt: '${h.format_short(created_localized)|n}',
+                    modifiedAt: '${h.format_short(updated_localized)|n}',
                     owner: '${result.file.owner.name}',
                     sourceLink: '${download_url}',
                     pdfAvailable: ${pdf_available}