Save new-shape feature-flag enable for 1.15.0

[johnkerl]

While recent PRs have put the release-1.15 branch in sync with current main, we shiould stop short of releasing the new-shape feature pending more documentation work as tracked on #2407 / [sc-51048].

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.90%. Comparing base (7b8190c) to head (531c30f).
Report is 1 commits behind head on release-1.15.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.15    #3260      +/-   ##
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+ Coverage         83.79%   83.90%   +0.10%     
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  Files                51       51              
  Lines              5560     5560              
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+ Hits               4659     4665       +6     
+ Misses              901      895       -6     

Flag	Coverage Δ
python	83.90% <100.00%> (+0.10%)	⬆️

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Components	Coverage Δ
python_api	83.90% <100.00%> (+0.10%)	⬆️
libtiledbsoma	∅ <ø> (∅)