imgui: bump imgui memory editor copy

imgui: bump imgui memory editor copy

Getting rid of a compiler warning :

In file included from ../src/intel/tools/aubinator_viewer.cpp:225:
../src/imgui/imgui_memory_editor.h: In member function ‘void MemoryEditor::DisplayPreviewData(size_t, const u8*, size_t, MemoryEditor::DataType, MemoryEditor::DataFormat, char*, size_t) const’:
../src/imgui/imgui_memory_editor.h:637:16: warning: enumeration value ‘DataType_COUNT’ not handled in switch [-Wswitch]
         switch (data_type)
                ^

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>