Minwaita-inkscape-dark is redundant

Summary:

Gtk can hold two versions of theme in one theme (that's why we have a dark mode switch). We ship Inkscape with Minwaita-Inkscape which holds a light and dark themes. Minwaita-inkscape-dark is redundant there is not good reason why we should ship Inkscape with this theme.

Sample attachments:

Version Info:

Inkscape 1.1-alpha (f11df71, 2021-03-31)

    GLib version:     2.68.0
    GTK version:      3.24.27
    glibmm version:   2.66.0
    gtkmm version:    3.24.3
    libxml2 version:  2.9.10
    libxslt version:  1.1.34
    Cairo version:    1.17.4
    Pango version:    1.48.4
    HarfBuzz version: 2.8.0
    Poppler version:  20.12.1

    OS version:       Windows 10 2009