Fix memory leak in D3MFOpcPackage

- closes https://github.com/assimp/assimp/issues/4628

code/AssetLib/3MF/D3MFOpcPackage.cpp

@@ -186,6 +186,9 @@ D3MFOpcPackage::D3MFOpcPackage(IOSystem *pIOHandler, const std::string &rFile) :
 D3MFOpcPackage::~D3MFOpcPackage() {
     mZipArchive->Close(mRootStream);
     delete mZipArchive;
+    for (auto tex : mEmbeddedTextures) {
+        delete mEmbeddedTextures[i];
+    }
 }
 
 IOStream *D3MFOpcPackage::RootStream() const {