Eliminate warnings re: CommandConfiguration init

[natecook1000]

When the old (pre-aliases) initializer has all its default parameter values, it is selected as the overload because it has fewer parameters overall. Removing the default parameters allows it to still satisfy (very niche) source compat requirements without actually being available as an overload.

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

[natecook1000]

@swift-ci Please test