fix: add the two includes clang-tidy reported as missing

misc-include-cleaner on the changed lines:
  TextureLibrary.cpp uses DecodedHeightTexture, which only reached it through
  TextureLibrary.hpp; it now includes libslic3r/TextureDisplacement.hpp itself.
  The contrast test uses std::not_equal_to, so <functional>.

src/slic3r/GUI/TextureLibrary.cpp

@@ -27,6 +27,7 @@
 #include <wx/mstream.h>
 
 #include "libslic3r/PNGReadWrite.hpp"
+#include "libslic3r/TextureDisplacement.hpp"
 #include "libslic3r/Utils.hpp"
 
 #include "libslic3r/AppConfig.hpp"

tests/libslic3r/test_texture_displacement.cpp

@@ -28,6 +28,7 @@
 
 #include <algorithm>
 #include <array>
+#include <functional>
 #include <cmath>
 #include <fstream>
 #include <limits>