test(mobile): use explicit expected values in isServer consistency test

[guesung]

Summary

• Replace relative assertions (toBe(secondCall)) with explicit expected values (toBe(false)) in isServer client-side consistency test
• Aligns with the pattern used in isServer.ssr.test.ts and getSafeAreaInset.ssr.test.ts

Test plan

• yarn test passes

[Copilot]

Pull request overview

Updates the isServer client-side consistency test to assert explicit expected values instead of comparing results across calls, aligning the test style with other SSR-related tests in the repo.

Changes:

• Replaced relative equality assertions (toBe(secondCall)) with explicit boolean expectations (toBe(false)) for isServer() repeated calls.

[kimyouknow]

LGTM!