fix(app): Show correct errors/warnings counts for schema validator

[nellh]

Correctly show the error and warning counts in the validation drop down.

Fixes #3263.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: packages/openneuro-app/src/scripts/validation/validation.tsx

Function	Unhandled Issue
Errors	ReferenceError: warnings is not defined /datasets... Event Count: 1 Affected Users: 1

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[codecov]

Codecov Report

Attention: Patch coverage is 54.54545% with 5 lines in your changes missing coverage. Please review.

Project coverage is 46.69%. Comparing base (042ce9c) to head (b80d887).
Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
...penneuro-app/src/scripts/validation/validation.tsx	54.54%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3270   +/-   ##
=======================================
  Coverage   46.68%   46.69%           
=======================================
  Files         609      609           
  Lines       38701    38704    +3     
  Branches     1225     1225           
=======================================
+ Hits        18068    18071    +3     
  Misses      20438    20438           
  Partials      195      195           

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[thinknoack]

reviewed local and ran tests. looks good.