Remove SSS jitter if TAA is off

com.unity.render-pipelines.high-definition/HDRP/Material/SubsurfaceScattering/SubsurfaceScattering.compute

 #endif
 
 #if SSS_RANDOM_ROTATION
-    float startAngle = TWO_PI * GenerateHashedRandomFloat(asuint(centerPosVS));
+    // Previously, we used asuint(centerPosVS) as the seed.
+    // This was not temporarily stable for some reason (pattern changed every frame),
+    // even if both the camera and the scene were completely static.
+    // Note that GenerateHashedRandomFloat() only uses the 23 low bits, hence the 2^24 factor.
+    float startAngle = TWO_PI * GenerateHashedRandomFloat(uint3(pixelCoord, (uint)(centerDepth * 16777216)));
 #else
     float startAngle = 0;
 #endif