fix: make sure runEither isn't calling itself

It looks like this was overlooked and the overloaded `runEither` is just
constantly calling itself resulting in a stack overflow. This changes it
to call the newly created `runEither` with the `nameMapper` which I
believe is the intended flow.

fixes #106

Author: ckipp01

mainargs/src/Parser.scala

@@ -213,7 +213,8 @@ class ParserForMethods[B](val mains: MethodMains[B]) {
     autoPrintHelpAndExit,
     customNames,
     customDocs,
-    sorted
+    sorted,
+    Util.kebabCaseNameMapper
   )
   @deprecated("Binary Compatibility Shim", "mainargs 0.6.0")
   def runRaw(