Add nvflare to requirements for ai_spleen_nnunet_seg_app

Author: SimoneBendazzoli93

examples/apps/ai_spleen_nnunet_seg_app/requirements.txt

@@ -7,6 +7,7 @@ numpy-stl>=2.12.0
 trimesh>=3.8.11
 nibabel>=3.2.1
 torch>=1.12.0
+nvflare
 git+https://github.com/SimoneBendazzoli93/dynamic-network-architectures.git
 git+https://github.com/SimoneBendazzoli93/MONAI.git@dev
 git+https://github.com/SimoneBendazzoli93/nnUNet.git