Remove Applications keyword from categories in grafx2.desktop

According to the current specs at https://specifications.freedesktop.org/menu-spec/latest/apa.html this is not a valid category (anymore).

misc/unix/grafx2.desktop

@@ -5,5 +5,5 @@ Exec=grafx2 %f
 Terminal=false
 Type=Application
 Icon=grafx2
-Categories=Application;Graphics;
+Categories=Graphics;
 MimeType=image/lbm;image/iff;image/pcx;image/tga;image/gif;image/bmp;image/x-icon;image/png;