Remove py3.6 reference from dispatcher

[gavin-aguiar]

Description

Ref: https://github.com/Azure/azure-functions-python-worker/issues/1038

Fixes #

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• [ ] 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.
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[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (dev@bcda54d). Click here to learn what that means. The diff coverage is 100.00%.

@@          Coverage Diff           @@
##             dev    #1056   +/-   ##
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  Coverage       ?   82.80%           
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  Files          ?       33           
  Lines          ?     1774           
  Branches       ?      282           
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  Hits           ?     1469           
  Misses         ?      234           
  Partials       ?       71           

Flag	Coverage Δ
unittests	82.80% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
azure_functions_worker/dispatcher.py	89.06% <100.00%> (ø)

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[gavin-aguiar]

in testutil_lc, also remove there? @gavin-aguiar

More changes are needed for this PR. Making it a draft for now