Always user unique cache key

[MartinRiese]

Product Description

Remove usage of cache key FF. Defaults to the FF behavior now.

Technical Summary

https://dimagi.atlassian.net/browse/USH-6540

Safety Assurance

FF has been released in production, enabling it for all projects. This just removes the check.

Safety story

Automated test coverage

Yes

QA Plan

None

Rollback instructions

• This PR can be reverted after deploy with no further considerations.

Review

• The set of people pinged as reviewers is appropriate for the level of risk of the change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.08%. Comparing base (14f69ec) to head (48f1ba5).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1773      +/-   ##
============================================
- Coverage     70.10%   70.08%   -0.03%     
+ Complexity     2030     2027       -3     
============================================
  Files           257      257              
  Lines          8011     8005       -6     
  Branches        764      763       -1     
============================================
- Hits           5616     5610       -6     
  Misses         2112     2112              
  Partials        283      283              

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[esoergel]

A few nitpicky comments, nothing breaking.