Cleanup: Add namespace to compositor.

source/blender/compositor/operations/COM_SetSamplerOperation.h

@@ -20,6 +20,8 @@
 
 #include "COM_NodeOperation.h"
 
+namespace blender::compositor {
+
 /**
  * this program converts an input color to an output Sampler.
  * it assumes we are in sRGB color space.
@@ -47,3 +49,5 @@ class SetSamplerOperation : public NodeOperation {
   void initExecution() override;
   void deinitExecution() override;
 };
+
+}  // namespace blender::compositor