Fix benign duplicate #140 insertion in asset map (#7855)

Co-authored-by: David Lowndes <David@DAVIDPCZ>

Author: Dave-Lowndes

src/surge-xt/gui/SkinImageMaps.h

@@ -116,7 +116,6 @@ inline std::unordered_set<int> allowedImageIds()
     allowed.insert(136);
     allowed.insert(137);
     allowed.insert(140);
-    allowed.insert(140);
     allowed.insert(143);
     allowed.insert(144);
     allowed.insert(145);