Metal: Remove warning about dummy attribute

This dummy attribute is never in an interface
and is there only to workaround the strict
requirement of a VBO in a GPUBatch.

source/blender/gpu/metal/mtl_batch.mm

@@ -157,11 +157,14 @@ int MTLBatch::prepare_vertex_binding(MTLVertBuf *verts,
         /* Vertex/instance buffers provided have attribute data for attributes which are not needed
          * by this particular shader. This shader only needs binding information for the attributes
          * has in the shader interface. */
-        MTL_LOG_WARNING(
-            "MTLBatch: Could not find attribute with name '%s' (defined in active vertex format) "
-            "in the shader interface for shader '%s'",
-            name,
-            interface->get_name());
+        if (StringRefNull(name) != "dummy") {
+          MTL_LOG_WARNING(
+              "MTLBatch: Could not find attribute with name '%s' (defined in active vertex "
+              "format) "
+              "in the shader interface for shader '%s'",
+              name,
+              interface->get_name());
+        }
         continue;
       }