Updated-readme-dependencies and a minor issue

[Abbsalehi]

Title: Fix PyTorch and Python Version in Installation Instructions

Description:

This pull request addresses and corrects the versions of PyTorch and Python specified in the installation instructions within the README and fixed a runtime error in demo_letr.ipynb. The following changes were made:

• Updated Python version to 3.8 in the conda environment creation command.
• Specified the versions of torch, torchvision, and torchaudio to be installed via pip.
• Ensured the instructions are clear and easy to follow.
• These changes aim to improve the accuracy of the installation instructions, ensuring that users can
  set up the environment without version compatibility issues.

Changes:

• Updated the conda create command to specify python=3.8.
• Updated the pip install command to install specific versions of torch, torchvision, and torchaudio:
  bash

pip install torch==1.8.1 torchvision==0.9.1 torchaudio==0.8.1

Testing:

Verified that the new installation instructions work as expected by setting up a new environment and running basic tests.

Additional Notes:

No other changes were made to the codebase.
Please review the updated instructions and provide feedback if any further adjustments are necessary.