Use transformed roughness instead of raw roughness to calculate roughness fade in SSR

(cherry picked from commit b99d0d778a)

servers/rendering/renderer_rd/shaders/effects/screen_space_reflection.glsl

@@ -237,7 +237,7 @@ void main() {
 
 		// This is an ad-hoc term to fade out the SSR as roughness increases. Values used
 		// are meant to match the visual appearance of a ReflectionProbe.
-		float roughness_fade = smoothstep(0.4, 0.7, 1.0 - normal_roughness.w);
+		float roughness_fade = smoothstep(0.4, 0.7, 1.0 - roughness);
 
 		// Schlick term.
 		float metallic = texelFetch(source_metallic, ssC << 1, 0).w;