Remove redundant nvml::Shutdown from optical flow (#5804)

- #5317 moved to scop based
  nvml init and shutdown, but a redundant shutdown has been
  left in the optical flow destructor. This PR removes it.

Signed-off-by: Janusz Lisiecki <[email protected]>

dali/operators/sequence/optical_flow/optical_flow.cc

@@ -55,7 +55,7 @@ The lower the speed, the more additional pre- and postprocessing is used to enha
 This operator produces the motion vector field at a coarser resolution than the input pixels.
 This parameter specifies the size of the pixel grid cell corresponding to one motion vector.
 For example, a value of 4 will produce one motion vector for each 4x4 pixel block. Hence, to
-use optical flow with an `output_grid` of 4 to resample a full resolution image, the flow field 
+use optical flow with an `output_grid` of 4 to resample a full resolution image, the flow field
 is upsampled *without* scaling the vector quantities.
 
 .. note::
@@ -184,11 +184,4 @@ void OpticalFlow<GPUBackend>::RunImpl(Workspace &ws) {
   }
 }
 
-template <>
-OpticalFlow<GPUBackend>::~OpticalFlow() {
-#if NVML_ENABLED
-  nvml::Shutdown();
-#endif
-}
-
 }  // namespace dali