Remove py3.6 reference from dispatcher

[gavin-aguiar]

Description

Ref: https://github.com/Azure/azure-functions-pyfx-planning/issues/139

Fixes #

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PR information

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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    Azure/azure-functions-python-worker#1056   +/-   ##
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  Coverage       ?   82.80%           
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  Files          ?       33           
  Lines          ?     1774           
  Branches       ?      282           
======================================
  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