Corrects variable name in max functions to better reflect usage

[dickoff]

The variable smallestThree should really be named largestThree. Looks like this was originally a copy paste error from the min documentation.

I noticed this error in the code section of the docs for max. This change only affects documentation and does not affect any actual code.

Checklist

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

[glessard]

@swift-ci please smoke test

[dickoff]

@swift-ci Please test