Bump development dependencies

[jakob-keller]

Description

Bump development dependencies while retaining Python 3.6 compatibility.

Checklist

• Add test cases to all the changes you introduce
• Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

Development dependencies are updated as far as Python 3.6 compatibility allows.

Steps to Test This Pull Request

Additional context

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.05 🎉

Comparison is base (f81f749) 98.02% compared to head (d50ed2c) 98.08%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #690      +/-   ##
==========================================
+ Coverage   98.02%   98.08%   +0.05%     
==========================================
  Files          40       40              
  Lines        1723     1723              
==========================================
+ Hits         1689     1690       +1     
+ Misses         34       33       -1     

Flag	Coverage Δ
unittests	98.08% <ø> (+0.05%)	⬆️

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

Impacted Files	Coverage Δ
commitizen/commands/check.py	100.00% <ø> (ø)
commitizen/hooks.py	95.65% <ø> (ø)

... and 1 file with indirect coverage changes

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