Fix alpha test condition to match glTF

src/Shaders/pbr.fragment.fx

@@ -277,7 +277,7 @@ void main(void) {
 
 #if !defined(LINKREFRACTIONTOTRANSPARENCY) && !defined(ALPHAFRESNEL)
 	#ifdef ALPHATEST
-		if (alpha <= ALPHATESTVALUE)
+		if (alpha < ALPHATESTVALUE)
 			discard;
 
 		#ifndef ALPHABLEND
@@ -405,7 +405,7 @@ void main(void) {
 			alpha = fresnelSchlickEnvironmentGGX(clamp(dot(viewDirectionW, normalForward), 0.0, 1.0), vec3(opacity0), vec3(opacity90), sqrt(microSurface)).x;
 
 			#ifdef ALPHATEST
-				if (alpha <= ALPHATESTVALUE)
+				if (alpha < ALPHATESTVALUE)
 					discard;
 
 				#ifndef ALPHABLEND