chore: Deprecates the DASHBOARD_CROSS_FILTERS feature flag

[michael-s-molina]

SUMMARY

As part of the 4.0 approved initiatives, this PR deprecates the DASHBOARD_CROSS_FILTERS feature flag which is currently True by default. The feature is already being used in production environments and we believe it's not something admins would want to disable.

TESTING INSTRUCTIONS

CI.

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

All modified and coverable lines are covered by tests ✅

Comparison is base (d5b62d8) 68.98% compared to head (f304755) 66.85%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #26633      +/-   ##
==========================================
- Coverage   68.98%   66.85%   -2.13%     
==========================================
  Files        1930     1930              
  Lines       75309    75309              
  Branches     8429     8429              
==========================================
- Hits        51949    50345    -1604     
- Misses      21213    22817    +1604     
  Partials     2147     2147              

Flag	Coverage Δ
javascript	56.48% <ø> (ø)
mysql	77.89% <ø> (ø)
postgres	77.99% <ø> (ø)
presto	?
python	78.12% <ø> (-4.45%)	⬇️
sqlite	77.57% <ø> (?)
unit	?

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[villebro]

LGTM after the rebase.