Update constant name value to result in FirstNonNil for clarity

[nkpgardose]

Hi Apple team, I am currently learning Swift and I am checking how things implemented on some Swift projects.

I made a very small change here, renaming value to result to give more clarity.

Thanks and have a good day.

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[ssouzawallace]

👀