Update preprocessing_tutorial.ipynb

Add comment: 
> Import all 3 Registrators 
> set ANTs as default

Author: evamariie

preprocessing/preprocessing_tutorial.ipynb

@@ -228,7 +228,11 @@
     "from brainles_preprocessing.brain_extraction import HDBetExtractor\n",
     "from brainles_preprocessing.modality import Modality\n",
     "from brainles_preprocessing.preprocessor import Preprocessor\n",
-    "from brainles_preprocessing.registration import NiftyRegRegistrator\n",
+    "from brainles_preprocessing.registration import ("
+    "    ANTsRegistrator #default",
+    "    NiftyRegRegistrator #support Linux",
+    "    eRegRegistrator #experimental",
+    "    )",
     "\n",
     "\n",
     "def preprocess_exam_in_brats_style(inputDir: str) -> None:\n",
@@ -319,7 +323,7 @@
     "        preprocessor = Preprocessor(\n",
     "            center_modality=center,\n",
     "            moving_modalities=moving_modalities,\n",
-    "            registrator=NiftyRegRegistrator(),\n",
+    "            registrator=ANTsRegistrator(),\n",
     "            brain_extractor=HDBetExtractor(),\n",
     "            # optional: we provide a temporary directory as a sandbox for the preprocessin\n",
     "            temp_folder=\"temporary_directory\",\n",