fix(ci): Fix root directory for size limit result upload

[Lms24]

Currently, CI is failing on develop because we specified the process.env object instead of a rootDir string as the third argument of the octokit uploadArtifact function. This PR fixes that by setting the directory of the results file as its root dir. I'm not a 100% convinced that this is correct but we'll see 🤞

(Also primes example why TypeScript is ❤️ )

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback)	80.76 KB (added)
@sentry/browser (incl. Tracing, Replay)	72.11 KB (added)
@sentry/browser (incl. Tracing, Replay with Canvas)	75.91 KB (added)
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	65.66 KB (added)
@sentry/browser (incl. Tracing)	36.71 KB (added)
@sentry/browser (incl. browserTracingIntegration)	36.71 KB (added)
@sentry/browser (incl. feedbackIntegration)	31.38 KB (added)
@sentry/browser (incl. feedbackModalIntegration)	31.49 KB (added)
@sentry/browser (incl. feedbackScreenshotIntegration)	31.5 KB (added)
@sentry/browser (incl. sendFeedback)	27.45 KB (added)
@sentry/browser	22.62 KB (added)
CDN Bundle (incl. Tracing, Replay, Feedback)	75.1 KB (added)
CDN Bundle (incl. Tracing, Replay)	69.93 KB (added)
CDN Bundle (incl. Tracing)	36.29 KB (added)
CDN Bundle	23.99 KB (added)
CDN Bundle (incl. Tracing, Replay) - uncompressed	219.67 KB (added)
CDN Bundle (incl. Tracing) - uncompressed	109.61 KB (added)
CDN Bundle - uncompressed	71.09 KB (added)
@sentry/react (incl. Tracing, Replay)	72.09 KB (added)
@sentry/react	22.64 KB (added)