[kotlin][client] Use Kotlin code style in parameter enum class names

[WonderCsabo]

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@jimschubert @dr4ke616 @karismann @Zomzog @andrewemery @4brunu @yutaka0m

[4brunu]

Hi @WonderCsabo, thanks for creating this PR.
The PR looks good overall.
I have one more request that is optional.
If you could also make this change on the other libraries in the Kotlin cliente generators, I would appreciate it, because that way all are coherent with each other.
https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator/src/main/resources/kotlin-client/libraries
Thanks

[WonderCsabo]

@4brunu sure thing! I updated the other kotlin-client libraries where i found this type of parameter type enum.

[4brunu]

Looks good to me, CI failure is not related to this PR 👍

[WonderCsabo]

@wing328 i guess this should be added to the 7.0.0 milestone instead.