COMP: Fix -Wdeprecated-declarations in ctkDICOMBrowserTester

This commit fixes the following warning:

/path/to/CTK/Libs/DICOM/Widgets/Testing/Cpp/ctkDICOMBrowserTest.cpp:79:49: warning: ‘QDir& QDir::operator=(const QString&)’ is deprecated: Use QDir::setPath() instead [-Wdeprecated-declarations]
   79 |   this->DICOMDir = dataDir.filePath("Data/DICOM");
      |                                                 ^

Libs/DICOM/Widgets/Testing/Cpp/ctkDICOMBrowserTest.cpp

@@ -76,7 +76,7 @@ void ctkDICOMBrowserTester::initTestCase()
   QDir dataDir = QDir(QProcessEnvironment::systemEnvironment().value("CTKData_DIR", ""));
   QVERIFY(dataDir.exists());
 
-  this->DICOMDir = dataDir.filePath("Data/DICOM");
+  this->DICOMDir.setPath(dataDir.filePath("Data/DICOM"));
   QVERIFY(this->DICOMDir.exists());
 
   this->DatabaseDirectoryName = QDir::tempPath() + "/ctkDICOMBrowserTest-Database";