Adds missing peer dependency

[arcanis]

apollo-link-error has a transitive peer dependency on graphql through apollo-link, and must be marked as such. Cf my article why implicit transitive peer dependencies are bad 🙂

As long as you're here, can you please give a look to the following related PRs? 😃

• apollo-engine-reporting
• apollo-cache
• @apollo/react-hooks
• @apollo/react-ssr

[apollo-cla]

@arcanis: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Apollo Contributor License Agreement here: https://contribute.apollographql.com/

[codecov-io]

Codecov Report

Merging #1196 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1196   +/-   ##
======================================
  Coverage    95.6%   95.6%           
======================================
  Files          22      22           
  Lines        1116    1116           
  Branches      174     162   -12     
======================================
  Hits         1067    1067           
  Misses         44      44           
  Partials        5       5

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[cometkim]

And there are few more; apollo-link-context also doesn't have peerDeps.

I can't use apollo with yarn 2 because of this. Any plan to update?