fix(browser): Remove import.meta.env check to avoid CJS syntax errors

The import.meta syntax causes 'Cannot use import.meta outside a module'
errors in CommonJS builds. Since the makeStripEsmPlugin that was supposed
to strip this code doesn't exist, removing the import.meta.env check entirely.

The SDK will still auto-enable Spotlight via:
- process.env: Works with Webpack, Next.js, CRA, Vite (with define config)
- globalThis: Works with Turbopack and other bundlers that inject at runtime

Also removed the related Vite spotlight-env tests since they were testing
the now-removed import.meta.env functionality.

Author: BYK