build: replace python 3.6 testing with 3.9

[hydrosquall]

CI was failing because Python 3.6 is no longer available in the test images. Replacing it with 3.9 instead.

[hydrosquall]

Current dependencies on/for this PR:

• master
  • PR build: replace python 3.6 testing with 3.9 #841 👈

This comment was auto-generated by Graphite.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (6a377f4) 90.47% compared to head (0642123) 90.47%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #841   +/-   ##
=======================================
  Coverage   90.47%   90.47%           
=======================================
  Files           6        6           
  Lines         294      294           
=======================================
  Hits          266      266           
  Misses         28       28           

Impacted Files	Coverage Δ
tiingo/api.py	93.18% <ø> (ø)
tiingo/wsclient.py	68.42% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.