Visibility settings labels should always be grabbed from mixins

mixins/Translations.vue offers some labels for visibility settings:

• me: Nobody except me
• instance: Everyone on this instance
• everyone: Everyone, across all instances

However, those labels are sometimes also hardcoded again in the different .vue files. To ensure maintanability, a consequent use of those labels across the App and make life easier for translators, those labels should always be grabbed from the mixin file.