Loosen tolerance on test

[willtebbutt]

Summary
Replaces an equality test with an approximate equality test to handle roundoff issues. Should resolve #494

Proposed changes
Loosen a test tolerance very slightly

What alternatives have you considered?
None

Breaking changes
None

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.25%. Comparing base (8746034) to head (9e30e87).
⚠️ Report is 60 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #495   +/-   ##
=======================================
  Coverage   94.25%   94.25%           
=======================================
  Files          52       52           
  Lines        1374     1374           
=======================================
  Hits         1295     1295           
  Misses         79       79           

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[willtebbutt]

@mjp98 if you could confirm that this seems to fix things on your end, I'll merge

[devmotion]

Is the non-standard rtol needed, in particular if we fix the seeds with StableRNGs? Maybe

Suggested change

	@test isapprox(
	kernelmatrix(k, x, y), kernelmatrix(k, collect(x), collect(y)); rtol=1e-6
	)
	@test kernelmatrix(k, x, y) ≈ kernelmatrix(k, collect(x), collect(y))

would be sufficient?