Modify Warning message about missing Depth for RenderTexture

The current Warning message when Depth is missing from RenderTexture is not helpful in identifying the source of the error and how to fix it. 
Updated this message for adding specific info about how to fix it.

Jira ticket: [UUM-73172](https://jira.unity3d.com/browse/UUM-73172)

Author: raquelpeces

Packages/com.unity.render-pipelines.universal/Runtime/2D/Rendergraph/Renderer2DRendergraph.cs

@@ -119,7 +119,7 @@ ImportResourceSummary GetImportResourceSummary(RenderGraph renderGraph, Universa
                 if (output.importInfoDepth.format == GraphicsFormat.None)
                 {
                     output.importInfoDepth.format = SystemInfo.GetGraphicsFormat(DefaultFormat.DepthStencil);
-                    Debug.LogWarning("Trying to render to a rendertexture without a depth buffer. URP+RG needs a depthbuffer to render.");
+                    Debug.LogWarning("In the render graph API, the output Render Texture must have a depth buffer. When you select a Render Texture in any camera's Output Texture property, the Depth Stencil Format property of the texture must be set to a value other than None.");
                 }
             }
             else

Packages/com.unity.render-pipelines.universal/Runtime/UniversalRendererRenderGraph.cs

@@ -559,7 +559,7 @@ void CreateRenderGraphCameraRenderTargets(RenderGraph renderGraph, bool isCamera
                 if (importInfoDepth.format == GraphicsFormat.None)
                 {
                     importInfoDepth.format = SystemInfo.GetGraphicsFormat(DefaultFormat.DepthStencil);
-                    Debug.LogWarning("Trying to render to a rendertexture without a depth buffer. URP+RG needs a depthbuffer to render.");
+                    Debug.LogWarning("In the render graph API, the output Render Texture must have a depth buffer. When you select a Render Texture in any camera's Output Texture property, the Depth Stencil Format property of the texture must be set to a value other than None.");
                 }
             }