Preparing nuspec file and pipeline changes for release

[vrdmr]

Description

Things changed in the PR:

• The nuspec files needed correction for Python 3.10 generation.
• Removed Tests section from azure-pipelines.yml as it wasn't required.
• Removed Python 3.6 generation and the V3 builds.
• Referencing the correct V4 nuspec.
• Also removed the need to install azure-functions in the pack/scripts/nix_deps.sh as we now made it as a required installation in setup.py.

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PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[codecov]

Codecov Report

Merging #966 (146dd61) into dev (65c30d8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #966   +/-   ##
=======================================
  Coverage   81.04%   81.04%           
=======================================
  Files          35       35           
  Lines        2337     2337           
  Branches      370      370           
=======================================
  Hits         1894     1894           
  Misses        337      337           
  Partials      106      106           

Flag	Coverage Δ
unittests	81.00% <ø> (ø)

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