refactor: Removes the deprecated VERSIONED_EXPORT feature flag

[michael-s-molina]

SUMMARY

As part of the 4.0 approved initiatives, this PR removes the VERSIONED_EXPORT feature flag.

The previous value of the feature flag was True and now the feature is permanently enabled.

TESTING INSTRUCTIONS

CI should be sufficient for merging this PR. We'll do a complete testing of 4.0 after all approved proposals are merged.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Attention: 64 lines in your changes are missing coverage. Please review.

Comparison is base (1010294) 69.56% compared to head (e2541e9) 67.25%.

Files	Patch %	Lines
superset/cli/importexport.py	61.72%	62 Missing ⚠️
superset/dashboards/api.py	94.44%	1 Missing ⚠️
superset/datasets/api.py	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #26347      +/-   ##
==========================================
- Coverage   69.56%   67.25%   -2.31%     
==========================================
  Files        1892     1892              
  Lines       74162    74107      -55     
  Branches     8263     8254       -9     
==========================================
- Hits        51593    49843    -1750     
- Misses      20488    22188    +1700     
+ Partials     2081     2076       -5     

Flag	Coverage Δ
hive	53.88% <25.12%> (+0.10%)	⬆️
javascript	56.85% <100.00%> (+<0.01%)	⬆️
mysql	78.05% <67.83%> (-0.16%)	⬇️
postgres	78.15% <67.83%> (-0.18%)	⬇️
presto	?
python	78.43% <67.83%> (-4.79%)	⬇️
sqlite	77.73% <67.83%> (-0.18%)	⬇️
unit	?

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[eschutho]

@michael-s-molina should we put in the PR description and UPDATING.md what the flag currently defaults to? I think that would help people know what behavior to expect.

[justinpark]

LGTM