Remove unnecessary specularmap_fragment include from physical shader

src/renderers/shaders/ShaderLib/meshphysical_frag.glsl

@@ -57,7 +57,6 @@ void main() {
 	#include <color_fragment>
 	#include <alphamap_fragment>
 	#include <alphatest_fragment>
-	#include <specularmap_fragment>
 	#include <roughnessmap_fragment>
 	#include <metalnessmap_fragment>
 	#include <normal_flip>