master to main urls (#720)

Author: rijobro

3d_segmentation/challenge_baseline/README.md

@@ -109,9 +109,9 @@ This baseline method achieves 0.6904 ± 0.1801 Dice score on the challenge valid
 
 - For MONAI technical documentation, please visit [docs.monai.io](https://docs.monai.io/).
 - Please visit [`Project-MONAI/tutorials`](https://github.com/Project-MONAI/tutorials) for more examples, including:
-  - [`3D segmentation pipelines`](https://github.com/Project-MONAI/tutorials/tree/master/3d_segmentation),
+  - [`3D segmentation pipelines`](https://github.com/Project-MONAI/tutorials/tree/main/3d_segmentation),
   - [`Dynamic UNet`](https://github.com/Project-MONAI/tutorials/blob/main/modules/dynunet_tutorial.ipynb),
-  - [`Training acceleration`](https://github.com/Project-MONAI/tutorials/tree/master/acceleration).
+  - [`Training acceleration`](https://github.com/Project-MONAI/tutorials/tree/main/acceleration).
 
 ## Submitting to the leaderboard
 

federated_learning/substra/README.md

@@ -1,6 +1,6 @@
 # MONAI on the Substra platform
 
-This examples demonstrates how to run the [3D segmentation tutorial](https://github.com/Project-MONAI/tutorials/tree/master/3d_segmentation) on the [Substra](https://github.com/substrafoundation/substra) platform.
+This examples demonstrates how to run the [3D segmentation tutorial](https://github.com/Project-MONAI/tutorials/tree/main/3d_segmentation) on the [Substra](https://github.com/substrafoundation/substra) platform.
 
 In order to run the example, you'll need to have an instance of the substra platform running. Please refer to the [Substra documentation](https://doc.substra.ai/) for more information.
 

modules/cross_validation_models_ensemble.ipynb

@@ -315,7 +315,7 @@
    "source": [
     "## Define a training process based on workflows\n",
     "\n",
-    "More usage examples of MONAI workflows are available at: [workflow examples](https://github.com/Project-MONAI/tutorials/tree/master/modules/engines)."
+    "More usage examples of MONAI workflows are available at: [workflow examples](https://github.com/Project-MONAI/tutorials/tree/main/modules/engines)."
    ]
   },
   {