fix(nextjs): Don't wrap res.json and res.send

[lforst]

Fixes #6670

By inspiration from axiom we wrapped all response methods in order to flush in a timely manner on AWS lambdas and Vercel. Turns out this is unnecessary because res.end is implicitly called by res.send and res.json so it is the only one we need to block.

Additionally wrapping send and json caused race conditions when they're called before .end because we turned them into async functions so end would sometimes be called before the other methods and prematurely terminatedthe response.

This PR removes the wrapping from res.json and res.end to fix the issues outlined above.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.85 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	61.46 KB (+0.03% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.62 KB (+0.02% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	55 KB (+0.02% 🔺)
@sentry/browser - Webpack (gzipped + minified)	20.38 KB (-0.05% 🔽)
@sentry/browser - Webpack (minified)	66.55 KB (-0.14% 🔽)
@sentry/react - Webpack (gzipped + minified)	20.4 KB (-0.03% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.67 KB (-0.03% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.82 KB (+0.03% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.25 KB (0%)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	43 KB (+0.03% 🔺)
@sentry/replay - Webpack (gzipped + minified)	38.25 KB (+0.04% 🔺)

[AbhiPrasad]

Is there a test that confirms this behaviour?