chore: remove additional incubator references

[amitmiran137]

SUMMARY

remove incubator.png from the main docs page
remove additional comments and docs references

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

before:

after:

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 #12336 (6cdc5a4) into master (076c31d) will decrease coverage by 3.61%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #12336      +/-   ##
==========================================
- Coverage   66.60%   62.98%   -3.62%     
==========================================
  Files        1002     1002              
  Lines       49330    49316      -14     
  Branches     5020     5020              
==========================================
- Hits        32855    31062    -1793     
- Misses      16333    18050    +1717     
- Partials      142      204      +62     

Flag	Coverage Δ
cypress	?
javascript	61.17% <ø> (ø)
python	64.16% <ø> (ø)

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

Impacted Files	Coverage Δ
...versions/f9a30386bd74_cleanup_time_grainularity.py	0.00% <ø> (ø)
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/chart/ChartContainer.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/reducers/index.js	0.00% <0.00%> (-100.00%)	⬇️
...et-frontend/src/dashboard/containers/Dashboard.jsx	0.00% <0.00%> (-100.00%)	⬇️
...t-frontend/src/explore/reducers/getInitialState.js	0.00% <0.00%> (-100.00%)	⬇️
...-frontend/src/visualizations/presets/MainPreset.js	0.00% <0.00%> (-100.00%)	⬇️
...tend/src/dashboard/containers/DashboardBuilder.jsx	0.00% <0.00%> (-100.00%)	⬇️
...c/visualizations/FilterBox/FilterBoxChartPlugin.js	0.00% <0.00%> (-100.00%)	⬇️
... and 163 more

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