MNT: Avoid jinja2 v3 until nbconvert handles breakages

[effigies]

Jinja2 is breaking everything for everybody. We don't directly depend on it, but nbconvert doesn't have fixes out yet.

Also, it seems setuptools stopped packaging data in 61.0.0.

xref jupyter/nbconvert#1737 pypa/setuptools#3196

[codecov]

Codecov Report

Merging #823 (ede7f96) into master (7af6c9e) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #823   +/-   ##
=======================================
  Coverage   85.94%   85.94%           
=======================================
  Files          35       35           
  Lines        3912     3914    +2     
  Branches     1001     1001           
=======================================
+ Hits         3362     3364    +2     
  Misses        357      357           
  Partials      193      193           

Impacted Files	Coverage Δ
bids/layout/layout.py	88.36% <0.00%> (+0.02%)	⬆️
bids/layout/index.py	84.98% <0.00%> (+0.05%)	⬆️

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