Pin Julia version for the Examples workflow

[odow]

Closes #862

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.76%. Comparing base (42bdbac) to head (6e121e0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #864      +/-   ##
==========================================
+ Coverage   96.75%   96.76%   +0.01%     
==========================================
  Files          56       56              
  Lines        9117     9117              
==========================================
+ Hits         8821     8822       +1     
+ Misses        296      295       -1     

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