optimize with precomputed kernel

Signed-off-by: lizzie <lizzie@eden-emu.dev>

src/video_core/host_shaders/present_lanczos.frag

@@ -18,7 +18,6 @@ const vec2 w_pos[49] = vec2[] (
 );
 const float w_sum = 21.045683f;
 vec4 textureLanczos(sampler2D textureSampler, vec2 p) {
-    const int r = 3; //radius (1 = 3 steps)
     vec3 c_sum = vec3(0.0f);
     vec2 res = vec2(textureSize(textureSampler, 0));
     vec2 cc = floor(p * res) / res;