🐛[RUMF-1276] handle performance entry without toJSON

[bcaudan]

Motivation

fix issue raised by telemetry

Changes

remove useless toJSON call and checks

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Merging #1751 (454dae8) into main (02d5b25) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1751      +/-   ##
==========================================
+ Coverage   91.03%   91.05%   +0.01%     
==========================================
  Files         128      128              
  Lines        4985     4984       -1     
  Branches     1113     1113              
==========================================
  Hits         4538     4538              
+ Misses        447      446       -1     

Impacted Files	Coverage Δ
...rumEventsCollection/resource/resourceCollection.ts	100.00% <100.00%> (+2.12%)	⬆️
packages/core/src/transport/batch.ts	93.02% <0.00%> (-1.17%)	⬇️
packages/core/src/tools/timeUtils.ts	100.00% <0.00%> (+2.56%)	⬆️

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