Update path to example data in notebooks

[w-k-jones]

Resolves #355

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f87ea1e) 55.75% compared to head (fbf2c06) 55.75%.

Additional details and impacted files

@@            Coverage Diff             @@
##           RC_v1.5.x     #357   +/-   ##
==========================================
  Coverage      55.75%   55.75%           
==========================================
  Files             15       15           
  Lines           3316     3316           
==========================================
  Hits            1849     1849           
  Misses          1467     1467           

Flag	Coverage Δ
unittests	55.75% <ø> (ø)

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[JuliaKukulies]

Thanks for fixing this quickly! So I guess we want to merge this one before #293