[pulsar-io-jdbc] not set action as insert (#4862)

### Motivation

jdbc sink treat all record as INSERT before #4358 , now it requires an indispensable action property which seems to be a break change, and we can deal records without any action property as INSERT.

### Modifications

treat action not set as INSERT action like before.
2 files changed
tree: 914a775ea8a6135006c36cfabff8c569c5d44ecf
  1. pulsar-io/