Avoid voxel cone trace from going full 180 degrees, fixes #20716

drivers/gles3/shaders/scene.glsl

@@ -1504,7 +1504,7 @@ void gi_probe_compute(mediump sampler3D probe, mat4 probe_xform, vec3 bounds, ve
 
 	//irradiance
 
-	vec3 irr_light = voxel_cone_trace(probe, cell_size, probe_pos, environment, blend_ambient, ref_vec, max(min_ref_tan, tan(roughness * 0.5 * M_PI)), max_distance, p_bias);
+	vec3 irr_light = voxel_cone_trace(probe, cell_size, probe_pos, environment, blend_ambient, ref_vec, max(min_ref_tan, tan(roughness * 0.5 * M_PI * 0.99)), max_distance, p_bias);
 
 	irr_light *= multiplier;
 	//irr_light=vec3(0.0);