[Backport 6000.0] Revert Changes from UUM-29958

I made a fix for https://jira.unity3d.com/browse/UUM-68986 that was too aggressive - clearing the material property block after each blit actually clears properties that are needed between blits, in the case for example of edge detection. This created another bug (https://jira.unity3d.com/browse/UUM-85970) where TexelSize property was cleared between two blits in the same pass.

Luckily, in the meantime, a better fix was implemented in Unity 6 and 7 (#51608)
This works better because it doesn't clear property blocks after each blit, only when a RenderTargetIdentifier is used, which is less aggressive than the fix I had in the first place

Packages/com.unity.render-pipelines.core/Runtime/Utilities/Blitter.cs

@@ -249,7 +249,6 @@ static internal void DrawTriangle(RasterCommandBuffer cmd, Material material, in
         static internal void DrawTriangle(CommandBuffer cmd, Material material, int shaderPass)
         {
             DrawTriangle(cmd, material, shaderPass, s_PropertyBlock);
-            s_PropertyBlock.Clear();
         }
 
         static internal void DrawTriangle(CommandBuffer cmd, Material material, int shaderPass, MaterialPropertyBlock propertyBlock)
@@ -273,7 +272,6 @@ static internal void DrawQuad(RasterCommandBuffer cmd, Material material, int sh
         static internal void DrawQuad(CommandBuffer cmd, Material material, int shaderPass)
         {
             DrawQuad(cmd, material, shaderPass, s_PropertyBlock);
-            s_PropertyBlock.Clear();
         }
 
         static internal void DrawQuad(CommandBuffer cmd, Material material, int shaderPass, MaterialPropertyBlock propertyBlock)