same shader fix but on the DropShadowScreenspace

Author: ninjamuffin99

source/funkin/graphics/shaders/DropShadowScreenspace.hx

@@ -128,7 +128,7 @@ class DropShadowScreenspace extends DropShadowShader
 
         float intensity = dot(col.rgb, vec3(0.3098, 0.6078, 0.0823));
 
-        intensity = maskIntensity > 0.0 ? intensity = float(intensity > thr2) : intensity = float(intensity > thr);
+        intensity = maskIntensity > 0.0 ? float(intensity > thr2) : float(intensity > thr);
 
         return intensity;
       }