UUM-48035: Fixed compiler error when using single precision caused from LightingSpecular

This PR fixes the compiler error, described in UUM-48035, when using `single` precision:

```
Shader error in 'Lights Receiver URP/LightsReceiver': Program 'frag', error X8000: D3D11 Internal Compiler Error: Invalid Bytecode: Incompatible min precision type for operand #3 of opcode #40 (counts are 1-based). Expected int or uint. at line 47 (on metal)
```

Author: jrs-unity

Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl

@@ -37,7 +37,8 @@ half3 LightingSpecular(half3 lightColor, half3 lightDir, half3 normal, half3 vie
     float3 halfVec = SafeNormalize(float3(lightDir) + float3(viewDir));
     half NdotH = half(saturate(dot(normal, halfVec)));
     half modifier = pow(float(NdotH), float(smoothness)); // Half produces banding, need full precision
-    half3 specularReflection = specular.rgb * modifier;
+    // NOTE: In order to fix internal compiler error on mobile platforms, this needs to be float3
+    float3 specularReflection = specular.rgb * modifier;
     return lightColor * specularReflection;
 }