test: Adjust data count range in SpotlightTests

[github-actions]

Note

The pull request "test: Adjust data count range in SpotlightTests" was created by @philipphofmann but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

Updated the expected data count range in the
SentrySpotlightTransportTests to allow for a wider variance in GZip compression results, changing the lower and upper bounds from ±20 to ±40 to avoid flakiness.

Test failed here https://github.com/getsentry/sentry-cocoa/actions/runs/18778698663/job/53579222897.

#skip-changelog

[linear]

COCOA-853