migrate: Migrate ExternalLinks component from enzyme to RTL

[EshaanAgg]

Which problem is this PR solving?

Fixes part of #1668

Description of the changes

Migrate ExternalLinks component from enzyme to RTL

How was this change tested?

Ran the tests locally

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: yarn lint and yarn test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3cc0e88) 96.54% compared to head (e192be6) 96.56%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2065      +/-   ##
==========================================
+ Coverage   96.54%   96.56%   +0.01%     
==========================================
  Files         255      255              
  Lines        7622     7622              
  Branches     1985     1985              
==========================================
+ Hits         7359     7360       +1     
+ Misses        263      262       -1     

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[yurishkuro]

Thanks!