Unify " for i18n function calls
Apparently when one uses ' for i18n functions, the PO files are not generated correctly.
Additionally, unifies the "Custom Emojis" text in the settings.
Something I noticed, is that whatever's generating the PO files takes into account whether i18n or i18nc was used and generates different text for each. For example, Configure NeoChat... is currently twice in the PO files, as once it's used as i18n("Configure NeoChat...") and once as i18nc("menu", "Configure NeoChat..."). Not sure whether this is intended, if not I can do another MR to unify them too.