README.txt - fix unreachable link (#2386)

Co-authored-by: sekyondaMeta <127536312+sekyondaMeta@users.noreply.github.com>

Author: noqqaqq

prototype_source/README.txt

@@ -1,8 +1,8 @@
 Prototype Tutorials
 ------------------
 1. distributed_rpc_profiling.rst
-     Profiling PyTorch RPC-Based Workloads
-     https://github.com/pytorch/tutorials/blob/release/1.6/prototype_source/distributed_rpc_profiling.rst
+           Profiling PyTorch RPC-Based Workloads
+           https://github.com/pytorch/tutorials/blob/main/prototype_source/distributed_rpc_profiling.rst
 
 2. graph_mode_static_quantization_tutorial.py
 	   Graph Mode Post Training Static Quantization in PyTorch
@@ -21,8 +21,8 @@ Prototype Tutorials
 	   https://github.com/pytorch/tutorials/blob/main/prototype_source/torchscript_freezing.py
 
 6. vulkan_workflow.rst
-     Vulkan Backend User Workflow
-     https://pytorch.org/tutorials/intermediate/vulkan_workflow.html
+           Vulkan Backend User Workflow
+           https://pytorch.org/tutorials/intermediate/vulkan_workflow.html
 
 7. fx_graph_mode_ptq_static.rst
 	   FX Graph Mode Post Training Static Quantization