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

valve/pbr/models/w_argrenade.mdl/w_argrenade.mat

@@ -0,0 +1,16 @@
+
+{
+"for" "#models/w_argrenade/Side1.mdl"
+//"basecolor_map" "Side1.png"
+//"normal_map" "Side1_normal.png"
+//"metal_map" "Side1_metal.png"
+//"roughness_map" "Side1_roughness.png"
+}
+
+{
+"for" "#models/w_argrenade/Tip1.mdl"
+//"basecolor_map" "Tip1.png"
+//"normal_map" "Tip1_normal.png"
+//"metal_map" "Tip1_metal.png"
+//"roughness_map" "Tip1_roughness.png"
+}