[doc] hotfix on sphinxcontrib-youtube package which causes readthedoc…

[tangxifan]

…s to fail

Motivate of the pull request

• To address an existing issue. If so, please provide a link to the issue:
• Breaking new feature. If so, please describe details in the description part.

Describe the technical details

What is currently done? (Provide issue link if applicable)

Currently, OpenFPGA has the following limitations:

• See the readthedocs build failures in recent PRs [engine] fixed a bug which causes errors when writing unique GSB to f… #755 [doc] hotfix on sphinxcontrib-youtube package which causes readthedoc… #1149

The error logs from readthedocs is pointing to the python package sphinxcontrib-yt, which is 3 year old.

[rtd-command-info] start-time: 2023-05-04T01:57:15.259507Z, end-time: 2023-05-04T01:57:16.259264Z, duration: 0, exit-code: 1
python -m pip install --exists-action=w --no-cache-dir -r docs/requirements.txt
Collecting sphinxcontrib-bibtex<2.0.0 (from -r docs/requirements.txt (line 9))
  Downloading sphinxcontrib_bibtex-1.0.0-py3-none-any.whl (14 kB)
Collecting sphinxcontrib-yt (from -r docs/requirements.txt (line 12))
  Downloading sphinxcontrib.yt-0.2.2.tar.gz (2.3 kB)
  Preparing metadata (setup.py): started
  Preparing metadata (setup.py): finished with status 'error'
  error: subprocess-exited-with-error
  
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [1 lines of output]
      ERROR: Can not execute `setup.py` since setuptools is not available in the build environment.
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

What does this pull request change?

This PR improves in the following aspects:

• Replace the sphinxcontrib-yt package with sphinxcontrib-youtube

Which part of the code base require a change

• VPR
• Tileable routing architecture generator
• OpenFPGA libraries
• FPGA-Verilog
• FPGA-Bitstream
• FPGA-SDC
• FPGA-SPICE
• Flow scripts
• Architecture library
• Cell library
• Documentation
• Regression tests
• Continous Integration (CI) scripts

Impact of the pull request

• Require a change on Quality of Results (QoR)
• Break back-compatibility. If so, please list who may be influenced.