Update apachepulsar/pulsar Docker tag to v3.1.2

This MR contains the following updates:

Package	Type	Update	Change
apachepulsar/pulsar		patch	3.1.1 -> 3.1.2
apachepulsar/pulsar	ironbank-docker	patch	3.1.1 -> 3.1.2
apachepulsar/pulsar	stage	patch	3.1.1 -> 3.1.2

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