use correct reh/reh-web package.json in bundle

[jmcphers]

This change addresses an issue in which Positron Server doesn't start due to an error like this one:

(node:11206) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/home/ubuntu/vscode-reh-web-linux-x64/out/server-main.js:26
export function __extends(d, b) {
^^^^^^

SyntaxError: Unexpected token 'export'
    at wrapSafe (node:internal/modules/cjs/loader:1378:20)
    at Module._compile 

The problem was caused by an incompletely merged line in the initial 1.95 merge, which caused a cascade of silent failures that led to package.json being omitted from the reh-web bundle, which led to the above failure since package.json was responsible for setting "type": "module" as noted above. The fix is just to update the line to match what it was before the merge:

positron/build/gulpfile.reh.js

Lines 378 to 383 in fa567b2

	// --- Start Positron ---
	// Note: The remote/reh-web/package.json is generated/updated in build/npm/postinstall.js
	const packageJsonBase = type === 'reh-web' ? 'remote/reh-web' : 'remote';
	const packageJsonStream = gulp.src([`${packageJsonBase}/package.json`], { base: packageJsonBase })
	.pipe(json({ name, version, dependencies: undefined, optionalDependencies: undefined, ...(isESM(`Setting 'type: module' in top level package.json`) ? { type: 'module' } : {}) })) // TODO@esm this should be configured in the top level package.json
	// --- End Positron ---

Addresses, coincidentally, #5775, which is where this error was first spotted.

After the change, it ought to be possible to run ./positron-server without error. E.g.:

./positron-server --version
Positron: 2025.01.1 build 4
Positron SHA: 9f520e6e796d266fcd603d601ae904e2abae8f9f
Code OSS: 1.96.0
Arch: arm64

[github-actions]

E2E Tests 🚀  ^?
This PR will run tests tagged with: @critical

[melissa-barca]

LGTM!

[sharon-wang]

Built reh-web locally and was able to do the following 👌

./positron-server --version
Positron: 2025.01.1 build 5
Positron SHA: d9090524f0920b313e1b6f085ca3db0fde1551ac
Code OSS: 1.96.0
Arch: x64