deprecate disable cache: no longer compatible with tests

[artoonie]

Disabling cache causes some tests which test caching to fail. Deprecate it: it doesn't help much of the time and is not worth maintaining for the little benefit it gives.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.06%. Comparing base (0b93708) to head (67723a5).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #617      +/-   ##
==========================================
+ Coverage   95.48%   96.06%   +0.57%     
==========================================
  Files         131      132       +1     
  Lines        6141     6298     +157     
==========================================
+ Hits         5864     6050     +186     
+ Misses        277      248      -29     

Files with missing lines	Coverage Δ
rcvis/settings.py	77.33% <100.00%> (+1.69%)	⬆️

... and 2 files with indirect coverage changes

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