chore(deps): update postgis/postgis docker tag to v15

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
postgis/postgis	final	major	14-3.3 -> 15-3.3
postgis/postgis	final	major	13-3.3 -> 15-3.3
postgis/postgis	final	major	12-3.3 -> 15-3.3

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