Summary:
this is a trivial change that allocates the NSMutableArray with the correct capacity before it is filled
## Changelog
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[Internal] [Changed] - RCTConvertVecToArray - allocate array with capacity
Pull Request resolved: https://github.com/facebook/react-native/pull/35490
Test Plan: tested locally: the code builds and runs as expected
Reviewed By: cipolleschi
Differential Revision: D41548050
Pulled By: GijsWeterings
fbshipit-source-id: a5b947331d6c5fffcfecc7c20c827f42442b1ab8
Vojtech Novak
e325c9505a