Update postgis/postgis Docker tag to v16

This MR contains the following updates:

Package	Type	Update	Change
postgis/postgis		major	15-3.4 -> 16-3.4
postgis/postgis	ironbank-docker	major	15-3.4-alpine -> 16-3.4-alpine
postgis/postgis	stage	major	15-3.4-alpine -> 16-3.4-alpine

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