specify precision for rectangular flashlight too

osu.Game.Resources/Shaders/sh_RectangularFlashlight.fs

@@ -1,10 +1,10 @@
 #include "sh_Flashlight.h"
 
-vec4 getColourAt(vec2 diff, vec2 size, vec4 originalColour)
+vec4 getColourAt(highp vec2 diff, highp vec2 size, lowp vec4 originalColour)
 {
     diff = abs(diff);
 
-    float alpha = length(smoothstep(size, size * smoothness, diff));
+    lowp float alpha = length(smoothstep(size, size * smoothness, diff));
 
     return originalColour * vec4(1.0, 1.0, 1.0, alpha);
 }