Fix: Memory leak in realtime compositor

There was a memory leak in the GPU code generator for the compositor
output. It was just due to a missing free in the GPU code generator
destructor, so this patch makes sure it is freed.

source/blender/gpu/intern/gpu_codegen.cc

@@ -259,6 +259,7 @@ class GPUCodegen {
     MEM_SAFE_FREE(output.volume);
     MEM_SAFE_FREE(output.thickness);
     MEM_SAFE_FREE(output.displacement);
+    MEM_SAFE_FREE(output.composite);
     MEM_SAFE_FREE(output.material_functions);
     delete create_info;
     BLI_freelistN(&ubo_inputs_);