Label and Label2 have encoding in their description tooltips

### Problem description

"Label" and "Label2" object properties have the encoding, namely `(UTF8)`, in their user facing descriptions. This is implementation detail, and only serves to confuse end users; the fields ought to work with *any* text the user can enter.

Handling of all string properties are slowly being migrated to UTF-8 anyway, so the distinction isn't even worth pointing out.

### Workbench affected?

Core (App, Gui,...)

### Steps to reproduce

Hover over either Label or Label2 in the properties pane.

### Expected behavior

No implementation detail to appear in the tooltips.

### Actual behavior

### Development version About Info (in Safe Mode)

Any

### Last known good version (optional)

None relevant, present since FreeCAD was migrated from SVN to `git`.

Start by locating the property definitions and user-facing descriptions for Label and Label2, then inspect how those descriptions appear in the properties pane tooltips. Done means the `(UTF8)` implementation detail is removed from both tooltips; verify by hovering over Label and Label2 in the properties pane.

Written by the indexing model from the issue text.