Prioritize pmc json

[lukuang]

According to the FAQs of the CORD-19 data set, we should use pmc json whenever possible, which were made available in recent releases.

[codecov]

Codecov Report

Merging #1101 into master will decrease coverage by 0.06%.
The diff coverage is 37.50%.

@@             Coverage Diff              @@
##             master    #1101      +/-   ##
============================================
- Coverage     46.61%   46.55%   -0.07%     
  Complexity      680      680              
============================================
  Files           143      143              
  Lines          8233     8242       +9     
  Branches       1168     1172       +4     
============================================
- Hits           3838     3837       -1     
- Misses         4056     4065       +9     
- Partials        339      340       +1     

Impacted Files	Coverage Δ	Complexity Δ
...o/anserini/collection/CovidCollectionDocument.java	38.70% <33.33%> (-7.45%)	5.00 <1.00> (ø)
.../anserini/collection/CovidParagraphCollection.java	83.33% <42.85%> (-6.38%)	3.00 <0.00> (ø)

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[lintool]

hi @lukuang just for completeness, can we keep the pdf_json copy?
@edwinzhng can you take a look please?

[edwinzhng]

Thanks for fixing! LGTM, ran it locally and it works

[lintool]

Waiting for @lukuang to revert the pdf_json copy and then I'll merge.

[lukuang]

Waiting for @lukuang to revert the pdf_json copy and then I'll merge.

Done. Please go ahead and ship.

[lintool]

Thanks @lukuang !