Remove gcc-13 build warning [-Wpessimizing-move]

Remove gcc-13 build warning [-Wpessimizing-move]

/home/leaf/work/dali-toolkit/dali-toolkit/internal/visuals/image-visual-shader-debug.cpp: In function ‘void Dali::Toolkit::Internal::ImageVisualShaderDebug::ApplyImageVisualShaderDebugScriptCode(std::string&)’:
/home/leaf/work/dali-toolkit/dali-toolkit/internal/visuals/image-visual-shader-debug.cpp:289:70: warning: moving a temporary object prevents copy elision [-Wpessimizing-move]
  289 |     RedefineMacro(fragmentShader, std::move(key.stringKey), std::move(value.Get<std::string>()));
      |                                                             ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/leaf/work/dali-toolkit/dali-toolkit/internal/visuals/image-visual-shader-debug.cpp:289:70: note: remove ‘std::mov’ call

Change-Id: I7327933872cca94879b39ab52f904f0d580d29b0
Signed-off-by: Eunki Hong <eunkiki.hong@samsung.com>