Remove unneeded write to .version file (facebook#39807)

Summary:

We used to need this file so that we could read the react native version when [creating Hermes artifacts](facebook@e4b5d3e#diff-78a8a19706dbd2a4425dd72bdab0502ed7a2cef16365ab7030a5a0588927bf47R1507). Originally, that change was introduced [here](facebook@e4b5d3e#diff-78a8a19706dbd2a4425dd72bdab0502ed7a2cef16365ab7030a5a0588927bf47)

Despite the fact that that approach was wrong, as we already have the right version in the package.json which is guaranteed to be present, a lot has changed since then and we don't need that file anymore.

## Changelog:
[Internal] - Remove lines that write a .version file while releasing on npm

Reviewed By: lunaleaps

Differential Revision: D49909718

scripts/publish-npm.js

@@ -81,10 +81,6 @@ function publishNpm(buildType) {
 
   generateAndroidArtifacts(version);
 
-  // Write version number to the build folder
-  const versionFile = path.join('build', '.version');
-  fs.writeFileSync(versionFile, version);
-
   if (buildType === 'dry-run') {
     echo('Skipping `npm publish` because --dry-run is set.');
     return exit(0);