fix: move seedrandom to dependency list

[markov00]

Summary

We are shipping the project with seedrandom as devDependency.
Since this is used in DataGenerator that is exposed as public module we should move the seedrandom devDependency to the dependency list.

see Jenkins errors in Kibana: https://kibana-ci.elastic.co/job/elastic+kibana+pipeline-pull-request/5354/console and the updating PR: elastic/kibana#47939

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• Any consumer-facing exports were added to src/index.ts (and stories only import from ../src except for test data & storybook)
• [ ] This was checked for cross-browser compatibility, including a check against IE11
• [ ] Proper documentation or storybook story was added for features that require explanation or tutorials
• [ ] Unit tests were updated or added to match the most common scenarios
• Each commit follows the convention

[codecov-io]

Codecov Report

Merging #423 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #423   +/-   ##
=======================================
  Coverage   97.85%   97.85%           
=======================================
  Files          39       39           
  Lines        2896     2896           
  Branches      701      701           
=======================================
  Hits         2834     2834           
  Misses         55       55           
  Partials        7        7

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[markov00]

close in favour of #424