[kotlin-spring] Adds 'suspend' modifier for reactive List endpoint with useFlowForArrayReturnType = false (#16130)

[hu553in]

Issue #16130

In previous PR 20409 I added new useFlowForArrayReturnType param, but unfortunately it was added with mistake. The thing is that List endpoints generated with useFlowForArrayReturnType = false must have suspend modifier; otherwise I have no possibility to call suspend service-layer (and other) functions from my controller (with useFlowForArrayReturnType = true I can call them when actually building Flow). This PR fixes that thing.

Technical committees

@dr4ke616 @karismann @Zomzog @andrewemery @4brunu @yutaka0m @stefankoppier @e5l

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[wing328]

that's ok. thanks for the follow-up PR, which has been merged

please pull the latest master to confirm it now works for your use cases.