Remove practically-unused `joblib`

[jwodder]

joblib.Memory was imported & instantiated in a few places, but nothing was done with it.

[codecov-commenter]

Codecov Report

Merging #360 (599410d) into master (a4c1ba2) will decrease coverage by 0.16%. The diff coverage is n/a.

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@@            Coverage Diff             @@
##           master     #360      +/-   ##
==========================================
- Coverage   33.63%   33.48%   -0.16%     
==========================================
  Files          50       50              
  Lines        7050     7040      -10     
  Branches     1781     1781              
==========================================
- Hits         2371     2357      -14     
- Misses       4500     4503       +3     
- Partials      179      180       +1     

Impacted Files	Coverage Δ
src/nidm/experiment/Query.py	71.73% <ø> (-0.16%)	:arrow_down:
src/nidm/experiment/tools/rest.py	70.24% <ø> (-0.18%)	:arrow_down:
src/nidm/experiment/tools/rest_statistics.py	17.64% <ø> (-8.67%)	:arrow_down:

... and 1 file with indirect coverage changes

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[yarikoptic]

seems LGTM, indeed those memory specs were added but not used even when added. probably copy pasted code from somewhere or used temporarily while debugging or smth like that. If actually to be come used -- should be easy to introduce

[github-actions[bot]]

:rocket: PR was released in v4.0.0 :rocket: