Fix failing Publish @react-native-community/template step (#45910)

Summary:
In build_npm_package, the publishing of the bumped template is [failing](https://github.com/facebook/react-native/actions/runs/10148492447/job/28063424722)
because it's running in sh instead of bash, but using bash syntax.

## Changelog: [Internal]

Pull Request resolved: https://github.com/facebook/react-native/pull/45910

Test Plan:
~~I'm unclear on how to test this, and the fix is very much speculative based on other having hit a similar issue.~~

I've had to stub some of the values that the action substitutes.

Reviewed By: cortinico

Differential Revision: D60828697

Pulled By: blakef

fbshipit-source-id: 0a8f909ae5219268f034e5ff0efb8acc94bdb7b1