fix(sveltekit): Remove invalid return in fetch proxy script

[Lms24]

(This bug didn't impact anyone as the fetch proxy script wasn't released yet)

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	75.16 KB (+0.41% 🔺)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	31.17 KB (+0.2% 🔺)
@sentry/browser - Webpack (gzipped)	21.85 KB (+0.19% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	69.73 KB (+0.27% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	28.18 KB (+0.11% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped)	20.18 KB (+0.06% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	219.89 KB (+0.38% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	84.78 KB (+0.13% 🔺)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	59.86 KB (+0.04% 🔺)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	31.04 KB (+0.09% 🔺)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	75.18 KB (+15.57% 🔺)
@sentry/react - Webpack (gzipped)	21.88 KB (+0.18% 🔺)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	92.97 KB (+0.35% 🔺)
@sentry/nextjs Client - Webpack (gzipped)	50.7 KB (+0.19% 🔺)