examples: fix usrsocktest compiler warning

[Gary-Hobson]

Summary

error: variable 'ret' set but not used [-Werror=unused-but-set-variable]
112 | int ret;

Impact

Testing

sim

[nuttxpr]

[Experimental Bot, please feedback here]

This PR does not meet the NuttX requirements.

Missing Information:

• Purpose of the Change: The summary only mentions a compiler error being fixed, but doesn't explain why the variable ret was unused in the first place.
  • Was it leftover code?
  • Did the logic change, making it obsolete?
• Impact Sections are Empty: You need to analyze and fill out all impact sections, even if the answer is "NO". Provide brief explanations when applicable.
• Insufficient Testing Details:
  • Build Host: Specify the OS, CPU architecture, and compiler version used for building.
  • "sim" is too vague: Which simulator? QEMU? Something else? Be specific about the simulated architecture and board configuration.
  • No "Before" Logs: Without seeing the error message in the "before" logs, it's impossible to verify the fix.

To Improve this PR:

1. Expand the Summary: Clearly explain the reason behind the unused variable and the fix.
2. Complete the Impact Assessment: Address each impact category, providing "NO" or a brief explanation if relevant.
3. Provide Detailed Testing Information: Include specifics about your build host, the exact simulator configuration, and the relevant "before/after" log snippets demonstrating the error and its resolution.

[xiaoxiang781216]

let's ignore ci check error which is fixed by #2712 to avoid wasting github resources.