x11-toolkits/gtk40: Fix PLIST

> Checking for items in STAGEDIR missing from pkg-plist

Error: Orphaned: @dir lib/gtk-4.0/%%GTK4_VERSION%%/engines
Error: Orphaned: @dir lib/gtk-4.0/%%GTK4_VERSION%%/loaders
Error: Orphaned: @dir lib/gtk-4.0/%%GTK4_VERSION%%/modules

> Checking for items in pkg-plist which are not in STAGEDIR

> Error: Plist issues found.

• Error code 1

Approved by: portmgr (blanket)