Removed NO_SHADOWS define as it's not really necessary. If one doesn't want shadow support only thing that needs to be done is to not define _SHADOWS_ENABLED or _LOCAL_SHADOWS_ENABLED in the shader.

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Shadows.hlsl

 
 half MainLightRealtimeShadowAttenuation(float4 shadowCoord)
 {
-#if defined(NO_SHADOWS) || !defined(_SHADOWS_ENABLED)
+#if !defined(_SHADOWS_ENABLED)
     return 1.0h;
 #elif SHADOWS_SCREEN
     return SampleScreenSpaceShadowMap(shadowCoord);
 
 half LocalLightRealtimeShadowAttenuation(int lightIndex, float3 positionWS)
 {
-#if defined(NO_SHADOWS) || !defined(_LOCAL_SHADOWS_ENABLED)
+#if !defined(_LOCAL_SHADOWS_ENABLED)
     return 1.0h;
 #else
     float4 shadowCoord = mul(_LocalWorldToShadowAtlas[lightIndex], float4(positionWS, 1.0));

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/LightweightStandardParticles.shader

             #pragma shader_feature _FADING_ON
             #pragma shader_feature _REQUIRE_UV2
 
-            #define NO_SHADOWS 1
-
             #include "LWRP/ShaderLibrary/ParticlesPBR.hlsl"
             #include "LWRP/ShaderLibrary/Lighting.hlsl"
 

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/LightweightStandardParticlesSimpleLighting.shader

             #pragma shader_feature _REQUIRE_UV2
 
             #define BUMP_SCALE_NOT_SUPPORTED 1
-            #define NO_SHADOWS 1
 
             #include "LWRP/ShaderLibrary/Particles.hlsl"
             #include "LWRP/ShaderLibrary/Lighting.hlsl"