[css-tables] Add spec link to 6 tests

[davidsgrogan]

Work toward making these pass the linter and get upstreamed to master.

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[w3c-bots]

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Lint

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Firefox (nightly channel)

Testing web-platform-tests at revision f26eb66
Using browser at version BuildID 20170418100213; SourceStamp bb38d935d699e0529f9e0bb35578d381026415c4
Starting 10 test iterations
No tests run.

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Chrome (unstable channel)

Testing web-platform-tests at revision f26eb66
Using browser at version 59.0.3071.9 dev
Starting 10 test iterations
No tests run.

[codecov-io]

Codecov Report

Merging #5615 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5615   +/-   ##
=======================================
  Coverage   87.22%   87.22%           
=======================================
  Files          24       24           
  Lines        2418     2418           
  Branches      406      406           
=======================================
  Hits         2109     2109           
  Misses        239      239           
  Partials       70       70

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