test(e2e): Migrate ErrorsScreen source assertion to sentry.segment.name.source

JS v11 removed the `sentry.source` semantic attribute; the transaction name
source now lives under `sentry.segment.name.source` on the segment span. The
navigation transaction's serialized `contexts.trace.data` therefore carries the
new key (matching the app-start unit snapshot already updated in this branch).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: antonis

samples/react-native/e2e/tests/captureErrorScreenTransaction/captureErrorsScreenTransaction.test.ts

@@ -74,7 +74,9 @@ describe('Capture Errors Screen Transaction', () => {
               'sentry.op': 'ui.load',
               'sentry.origin': 'auto.app.start',
               'sentry.sample_rate': 1,
-              'sentry.source': 'component',
+              // JS v11 removed `sentry.source`; the transaction name source now
+              // lives under `sentry.segment.name.source` on the segment span.
+              'sentry.segment.name.source': 'component',
               'thread.name': 'javascript',
             }),
             op: 'ui.load',