Decrease stack-safety test size

[edmundnoble]

Locally looping 60000-deep in a recursive function is enough to blow my stack; as it is, these tests still fail on my machine with Eval swapped for Id.

[codecov-io]

Codecov Report

Merging #1760 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1760   +/-   ##
=======================================
  Coverage   94.17%   94.17%           
=======================================
  Files         256      256           
  Lines        4208     4208           
  Branches       93       93           
=======================================
  Hits         3963     3963           
  Misses        245      245

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[edmundnoble]

Notably decreases test duration on CI:
before @peterneyens' PR
@peterneyens' PR
this PR

I don't know if/how translates to a lower average total test time.