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

valve/pbr/models/concrete_gibs.mdl/concrete_gibs.mat

@@ -0,0 +1,32 @@
+
+{
+"for" "#models/concrete_gibs/c1.mdl"
+//"basecolor_map" "c1.png"
+//"normal_map" "c1_normal.png"
+//"metal_map" "c1_metal.png"
+//"roughness_map" "c1_roughness.png"
+}
+
+{
+"for" "#models/concrete_gibs/c2.mdl"
+//"basecolor_map" "c2.png"
+//"normal_map" "c2_normal.png"
+//"metal_map" "c2_metal.png"
+//"roughness_map" "c2_roughness.png"
+}
+
+{
+"for" "#models/concrete_gibs/c3.mdl"
+//"basecolor_map" "c3.png"
+//"normal_map" "c3_normal.png"
+//"metal_map" "c3_metal.png"
+//"roughness_map" "c3_roughness.png"
+}
+
+{
+"for" "#models/concrete_gibs/c4.mdl"
+//"basecolor_map" "c4.png"
+//"normal_map" "c4_normal.png"
+//"metal_map" "c4_metal.png"
+//"roughness_map" "c4_roughness.png"
+}