build: Set Volta Node.js version to 18

[lforst]

CI keeps flaking on us on what it seems like a node/v8 bug. Let's revert to 18 to fix.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	75.35 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	66.75 KB (-0.02% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	60.35 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	31.39 KB (-0.1% 🔽)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	30.04 KB (+0.05% 🔺)
@sentry/browser - Webpack (gzipped)	21.69 KB (-0.15% 🔽)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	72.78 KB (+0.06% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	64.5 KB (+0.07% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	30.71 KB (-0.08% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped)	22.77 KB (-0.08% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	202.34 KB (-0.12% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	92.28 KB (-0.43% 🔽)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	67.34 KB (-0.57% 🔽)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	33.62 KB (+0.11% 🔺)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	67.13 KB (+0.01% 🔺)
@sentry/react - Webpack (gzipped)	21.72 KB (-0.17% 🔽)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	83.89 KB (-0.03% 🔽)
@sentry/nextjs Client - Webpack (gzipped)	48.57 KB (-0.03% 🔽)
@sentry-internal/feedback - Webpack (gzipped)	16.35 KB (0%)

[anonrig]

Did this change fix the original issue? Node 20 is in LTS.

[lforst]

@anonrig Yes this fixed it. CI was basically unusable while we had it set to node 20.