remove combined {models,sprites}.mat, remove extra .mdl .spr exts

gearbox/pbr/models/w_penguinnest.mdl/w_penguinnest.mat

@@ -0,0 +1,16 @@
+
+{
+"for" "#models/w_penguinnest/sign.mdl"
+//"basecolor_map" "sign.png"
+//"normal_map" "sign_normal.png"
+//"metal_map" "sign_metal.png"
+//"roughness_map" "sign_roughness.png"
+}
+
+{
+"for" "#models/w_penguinnest/snow_man.mdl"
+//"basecolor_map" "snow_man.png"
+//"normal_map" "snow_man_normal.png"
+//"metal_map" "snow_man_metal.png"
+//"roughness_map" "snow_man_roughness.png"
+}