Set ss shadowmap RT format back to R8 from debug visualize.

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

             SetupShadowReceiverConstants(cmd, visibleLights[lightData.mainLightIndex]);
             SetShadowCollectPassKeywords(cmd, ref lightData);
 
-            cmd.GetTemporaryRT(m_ScreenSpaceShadowMapRTID, m_CurrCamera.pixelWidth, m_CurrCamera.pixelHeight, 0, FilterMode.Bilinear, RenderTextureFormat.ARGBHalf);
+            cmd.GetTemporaryRT(m_ScreenSpaceShadowMapRTID, m_CurrCamera.pixelWidth, m_CurrCamera.pixelHeight, 0, FilterMode.Bilinear, RenderTextureFormat.R8);
             cmd.Blit(null, m_ScreenSpaceShadowMapRT, m_ScreenSpaceShadowsMaterial);
 
             context.ExecuteCommandBuffer(cmd);

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/LightweightScreenSpaceShadows.shader

             return o;
         }
 
-        half4 Fragment(Interpolators i) : SV_Target
+        half Fragment(Interpolators i) : SV_Target
         {
             UNITY_SETUP_INSTANCE_ID(i);