fix: update latest tag action to use set-output

[eschutho]

SUMMARY

GitHub recently deprecated set-env with their latest actions security updates. This replaces set-env with set-output
https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

TEST PLAN

manually tested with nektos/act utility

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[eschutho]

@dpgaspar @villebro @ktmud

[codecov-io]

Codecov Report

Merging #12706 (9b144c6) into master (b8a93fd) will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #12706      +/-   ##
==========================================
+ Coverage   66.79%   66.88%   +0.08%     
==========================================
  Files        1019     1019              
  Lines       49824    49825       +1     
  Branches     4877     4877              
==========================================
+ Hits        33281    33323      +42     
+ Misses      16419    16379      -40     
+ Partials      124      123       -1     

Flag	Coverage Δ
cypress	50.94% <ø> (+1.34%)	⬆️
javascript	60.93% <ø> (ø)
python	64.05% <ø> (-0.10%)	⬇️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/presto.py	82.25% <0.00%> (-6.28%)	⬇️
superset/models/core.py	88.58% <0.00%> (-0.28%)	⬇️
superset-frontend/src/SqlLab/actions/sqlLab.js	62.42% <0.00%> (+0.21%)	⬆️
superset/datasets/commands/importers/v1/utils.py	56.16% <0.00%> (+0.60%)	⬆️
superset-frontend/src/reduxUtils.ts	79.74% <0.00%> (+1.26%)	⬆️
...set-frontend/src/dashboard/util/getDropPosition.js	93.65% <0.00%> (+1.58%)	⬆️
...e/components/controls/FilterControl/AdhocFilter.js	96.92% <0.00%> (+3.07%)	⬆️
superset-frontend/src/SqlLab/components/App.jsx	64.28% <0.00%> (+7.14%)	⬆️
...nd/src/dashboard/components/gridComponents/Tab.jsx	74.07% <0.00%> (+7.40%)	⬆️
...c/dashboard/components/gridComponents/Markdown.jsx	90.38% <0.00%> (+7.69%)	⬆️
... and 7 more

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