KSP: Fixed method isEnum() for KotlinTypeArgumentElement

[altro3]

No description provided.

[altro3]

@dstepanov Review it, pls. Found this problem in simple test in micronaut-openapi:

@Controller("/hello")
class HelloController {

    @Get
    @Produces(MediaType.TEXT_PLAIN)
    fun index(@Nullable @QueryValue("channels") channels: Collection<Channel?>?) = ""

    @Introspected
    enum class Channel {
        @JsonProperty("mysys")
        SYSTEM1,
        SYSTEM2
    }
}

When I get typeArgument for Collection type, I get KotlinTypeArgumentElement element, and default isEnum() implemention is

    default boolean isEnum() {
        return this instanceof EnumElement;
    }

That's why method isEnum() returns false, but must be true