[js/rn] Fix extensions header include issue (#15800)
### Description
<!-- Describe your changes. -->
Identified the cause for a `redefinition compilation error` happened in
a react native expo app with ort-extensions enabled when running the ios
side. Fix the include path now, so we can remove the temporary forward
declaration in OnnxruntimeModule.mm file.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Fix implementation detail.
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Co-authored-by: rachguo <rachguo@rachguos-Mini.attlocal.net>
