Add a lock file for requirements-docs.txt

[jonathan343]

This PR uses the pip-compile command from pip-tools to generate a lock file for requirments-docs.txt. This was generated in Python 3.8 virtual environment.

NOTE: The following urllib3 requirements were added to requirements-docs.txt to force the same version constraints as botocore when generating the requirements-docs-lock.txt:

urllib3>=1.25.4,<1.27 ; python_version < "3.10"
urllib3>=1.25.4,!=2.2.0,<3 ; python_version >= "3.10"

This specifically becomes an issue when using Python 3.8 since Sphinx has a transitive dependency on the latest version of urllib3 and botocore will require urllib3>=1.25.4,<1.27.

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.14%. Comparing base (b4a86ed) to head (826d79a). Report is 33 commits behind head on develop.

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Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3208   +/-   ##
========================================
  Coverage    93.14%   93.14%           
========================================
  Files           66       66           
  Lines        14248    14248           
========================================
  Hits         13272    13272           
  Misses         976      976           

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