fix: adding nofollow to 3rd party links on docs site

[rusackas]

SUMMARY

Apache prefers we add the 'nofollow' flag, so folks know we're unaffiliated.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

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

[codecov-io]

Codecov Report

Merging #11225 into master will decrease coverage by 4.15%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #11225      +/-   ##
==========================================
- Coverage   65.50%   61.34%   -4.16%     
==========================================
  Files         830      831       +1     
  Lines       39258    39292      +34     
  Branches     3593     3592       -1     
==========================================
- Hits        25714    24102    -1612     
- Misses      13432    15009    +1577     
- Partials      112      181      +69     

Flag	Coverage Δ
#cypress	?
#javascript	62.40% <ø> (+0.02%)	⬆️
#python	60.70% <ø> (ø)

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

Impacted Files	Coverage Δ
superset-frontend/src/SqlLab/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/dashboard/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/index.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/dashboard/index.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupColors.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/chart/ChartContainer.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupFormatters.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/reducers/index.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupPluginsExtra.js	0.00% <0.00%> (-100.00%)	⬇️
... and 170 more

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