Quiet known warnings in tests

[pathawks]

Every time I test, I see

Randomized with seed 16380
............................Validation warning: Two entries with the same value for atom:updated on line 5 column 239
Validation warning: content should not be blank on line 5 column 898
Validation warning: summary should not be blank on line 5 column 917
.

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29 examples, 0 failures

These warnings are just noise. The content and summary warnings come from a test case that checks for blank content. The warning about duplicate atom:updated values is just because several files were added to the git repo at once.

I want to make sure that nothing we change accidentally introduces new warnings.

These expected warnings are just ignored, and so should not even appear in the test output.

[parkr]

❤️

@jekyllbot: merge +dev