fix(utils): Remove circular dependency in instrument

[AbhiPrasad]

Instead of importing from the index, import directly from the file itself. This was causing warnings when bundling with rollup.

[github-actions]

size-limit report

Path	Base Size (3d48c93)	Current Size	Change
@sentry/browser - CDN Bundle (gzipped)	19.72 KB	19.72 KB	+0.02% 🔺
@sentry/browser - CDN Bundle (minified)	62.76 KB	62.77 KB	+0.01% 🔺
@sentry/browser - Webpack	22.25 KB	22.25 KB	-0.01% 🔽
@sentry/browser - Webpack - gzip = false	75.92 KB	75.92 KB	0%
@sentry/react - Webpack	22.29 KB	22.29 KB	-0.01% 🔽
@sentry/nextjs Client - Webpack	46.41 KB	46.41 KB	+0.01% 🔺
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	28.37 KB	28.38 KB	+0.01% 🔺