Fix shader precision (#19695)

Resources/Textures/Shaders/hcut.swsl

@@ -7,7 +7,7 @@ const bool below = true;
 void fragment()
 {
     highp vec4 tex = zTexture(UV);
-    highp float modifier = (UV.y > c ^^ !below) ? 1 : alphaModifier;
+    highp float modifier = (UV.y > c ^^ !below) ? 1.0f : alphaModifier;
 
     COLOR = vec4(tex.x, tex.y, tex.z, tex.w * modifier);
 }