starboard: Remove dead Evergreen Lite guards

[hferreiro]

SB_IS(EVERGREEN_COMPATIBLE_LITE) has not been defined since the sb_evergreen_compatible_enable_lite GN arg was removed in 10b7c61. Evergreen Lite is selected at runtime with the --evergreen_lite loader flag.

Bug: 272635054

[github-actions]

Context	State	Description
CI / android	❌ FAIL	Failed
CI / aosp	✅ PASS	Passed
CI / evergreen	❌ FAIL	Failed
CI / linux	❌ FAIL	Failed
CI / tvos	✅ PASS	Passed
import/copybara	✅ PASS	Change imported to Gerrit
kokoro	✅ PASS	Kokoro build finished

[github-actions]

🤖 Gemini Suggested Commit Message

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starboard: Remove dead Evergreen Lite guards

The SB_IS(EVERGREEN_COMPATIBLE_LITE) macro is no longer defined since
the sb_evergreen_compatible_enable_lite GN argument was removed in a
previous commit. Evergreen Lite is now selected at runtime using the
--evergreen_lite loader flag, making these compile-time guards
obsolete.

This update cleans up the codebase by removing unused preprocessor
logic and updating the documentation to reflect the current
configuration process.

Bug: 272635054

---

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[gemini-code-assist]

Code Review

This pull request simplifies the Evergreen configuration by removing the EVERGREEN_COMPATIBLE_LITE preprocessor guards and configuration options across documentation and source files, making the pending restart functionality standard. The review feedback suggests improving the grammatical phrasing in the updated documentation files for better readability.